Seat

ABSTRACT

At a vehicle seat  10 , a cushion material  18  is provided at a frame  14  for a sitting portion of a seat frame  12 , such that a seat cushion  20  is formed. An upper cushion member (three-dimensional solid knit fabric)  86 , which is a surface layer portion of the cushion material  18 , is stretched at the frame  14  for the sitting portion, and is layered on a cloth spring material  18  which is a lower layer portion of the cushion material  18 . When the cloth spring material  68  is pressed and flexes downward due to pushing-against force which is based on body weight of a seated person at a time of sitting on the seat cushion  20 , at regions of the cloth spring material  68  which are pushed by ischial tuberosities of the seated person, tensile forces of extension coil springs  80 , which are forces in the pushing direction, act, and directions of tension of the cushion material  18  are in three dimensions.

TECHNICAL FIELD

The present invention relates to a seat, and in particular, to a seatsuch as a vehicle seat which is installed in a vehicle, or the like.

BACKGROUND ART

There is conventionally known, as a vehicle seat, a vehicle seat havinga cushion material formed from polyurethane foam (hereinafter calledurethane). As the cushion structure of such a vehicle seat, a structureis widely used in which a cushion material made of urethane is placed ona plate or a spring material, such as a contour mat (trade name) or thelike provided at a seat frame or a seat back frame, and these arewrapped in a fabric material.

Therefore, it is known that the shape (the design shape) and the elasticcharacteristic of the cushion material have a great effect on the bodypressure dispersability of the seated person and the vibrationabsorbability. Further, by structuring the cushion material by layeringurethanes which have various characteristics, a cushion material can beobtained which has a spring characteristic (elastic characteristic)which is near the spring characteristic of the muscles of the buttocksor the like of the seated person. However, in such a structure, thereare the problems that there is the sensation that the restoring force isinsufficient and that the weight is heavy.

Thus, a seat has been conceived of in which, as the cushion materialtaking the place of urethane, a cushion structure is structured bystretching, over a seat frame, a pair of ground knit fabrics and atwo-dimensional knit fabric or a three-dimensional solid knit fabricformed by connecting threads which are disposed between the groundfabrics (see, for example, Japanese Patent No. 5013089). The cushionmaterial formed from this three-dimensional solid knit fabric ortwo-dimensional fabric is an elastic structure which is difficult toweaken, and is thinner than urethane, and exhibits an elasticcharacteristic in place of urethane.

However, in a conventional vehicle seat using such a three-dimensionalsolid knit fabric or two-dimensional fabric as the cushion material, thetwo-dimensional knit fabric is stretched over the seat frame at atension such that the elongation is in the range of from 5% to 20%, andthe three-dimensional solid knit fabric is stretched at a tension suchthat the elongation is less than 5%. Therefore, when a person sits down,large forces arise due to tension at the portions where the convexportions of the human body, such as the ischia, the coccyx, the shoulderblades and the like, contact the cushion material (clothes are ignored).Therefore, this becomes a cause of the supporting pressure becomingstrong and a sensation that a foreign object exists arising. Further, ifthis acts over a long time period, there is the problem that pain arisesin the muscles at the peripheries of the aforementioned ischia, coccyx,shoulder blades and the like. In particular, the muscles and the bloodvessels in the peripheries beneath the ischial tuberosities, whichsupport the majority of the body weight of the human body, arecompressed, and there are cases in which pain or numbness due tointerruption in blood circulation arises.

Further, in the above-described conventional seat, the two-dimensionalknit fabric is stretched directly over the frame. Therefore, the problemis known that it is easy for there to arise a phenomenon, which is theso-called hammock sensation phenomenon, in which it is easy for theseated person to move in the front-rear and left-right directions withinthe frame, and due to the input of vibration at the time when thevehicle travels for example, the seated posture of the seated personchanges or the seated person slides forward on the seat.

DISCLOSURE OF THE INVENTION

Thus, the present invention overcomes the above-described problems asfollows.

A seat which is a first aspect of the present invention comprises: aseat frame having a frame for a sitting portion and a frame for a backportion; a planar tension structure attached to the frame for thesitting portion or the frame for the back portion; and an elasticsupporting structure supporting the planar tension structure, betweenthe frame for the sitting portion or the frame for the back portion andthe planar tension structure, such that directions of tension are inthree dimensions.

In the seat which is the first aspect of the present invention, theplanar tension structure, which is supported at the frame for thesitting portion via the elastic supporting structure, structures atleast a portion of a cushion material of a seat cushion, and the planartension structure, which is supported at the frame for the back portionvia the elastic supporting structure, structures at least a portion of acushion material of a seat back.

Incidentally, among human bodies (seated persons), individualdifferences are great, physical abilities and seated postures alsodiffer, and the ways of coping with seating over a long time period alsodiffer. Further, the respective regions of a human body exhibit athree-dimensional configuration and are structured by many parameters,and among these parameters, the individual differences with respect tothe dynamic characteristics of the muscles in particular are great.Moreover, at the respective regions of the human body, the respectiveparameters vary as, for example, the human body swings due to thebehavior of the vehicle while traveling. Therefore, in order tostabilize the seated posture while mitigating pain and numbness of theseated person, it is effective to make the compliance of the seatcushion or the seat back conform to (match) the compliance of the humanbody. Note that compliance is defined as (amount of flexure)/(pressurevalue).

Here, in the seat which is the first aspect of the present invention,the planar tension structure which is two-dimensional is elasticallysupported by the elastic supporting structure at least one of the framefor the sitting portion and the frame for the back portion of the seatframe, such that the directions of tension are in three dimensions. Inother words, force (pseudo normal line direction force) in a directionintersecting the tensile force in a case of being supportedtwo-dimensionally, is applied to the planar tension structure by theelastic supporting structure.

Therefore, at the seat cushion or the seat back, a human body, which isa three-dimensional pressure applying body, can be supported by pseudonormal line direction force. In addition, because a low tension portionand a high tension portion (tension fields) are generated at the planartension structure due to the three-dimensional support by the elasticsupporting structure, the compliance (elastic characteristic) of thatplanar tension structure (the seat cushion or the seat back) can be setto conform to the compliance of the human body. Namely, although itsuffices for the elastic supporting structure to support the planartension structure three-dimensionally at the time of sitting, theelastic supporting structure may support the planar tension structuresuch that the planar tension structure is a three-dimensionalconfiguration before sitting. This tension may be formed of tensionwhich supports the planar tension structure two-dimensionally, and thepseudo normal line direction force which is force in a directionintersecting that tension. Further, the direction of the pseudo normalline direction force may be a direction running along a vertical planewhich includes the front-rear direction of the seat.

In this way, the seat which is the first aspect of the present inventioncan stabilize the seated posture while mitigating pain and numbness ofthe seated person.

In a seat which is a second aspect of the present invention, in the seatwhich is the first aspect of the present invention, the elasticsupporting structure includes a first elastic member which, at a time ofsitting, pulls a rear end of the planar tension structure, whose frontend is fixed to the frame for the sitting portion, rearward while movingthe rear end forward.

In the seat which is the second aspect of the present invention, theplanar tension structure, whose front end is fixed to the frame for thesitting portion, structures at least a portion of the cushion materialof the seat cushion. When the planar tension structure flexes downwarddue to the pressure by the human body at the time of sitting, the rearend of that planar tension structure is, by the first elastic member,pulled rearward while moving forward. Therefore, the tension around thesacral bone of the seated person at the time of sitting is small ascompared with a case in which the first elastic member is not provided,and the fitting sensation improves.

Further, due to this decrease in tension, matching of the compliance ofthe planar tension structure (the seat cushion) and the compliance ofthe human body is aimed for, and a reduction in pain and numbness aroundthe ischial tuberosities is possible. Moreover, due to this decrease intension, the absorbability of impact vibrations and vibrations of theentire body of the seated person, which are caused by top-bottomdirection vibrations, is improved.

In a seat which is a third aspect of the present invention, in the seatwhich is the first aspect of the present invention, the elasticsupporting structure includes a second elastic member which is providedbetween the frame for the sitting portion and the planar tensionstructure, and which, at a time of sitting, pulls downward vicinities ofbeneath ischial tuberosities of a seated person at the planar tensionstructure.

In the seat which is the third aspect of the present invention, theplanar tension structure structures at least a portion of the cushionmaterial of the seat cushion, and portions, at the planar tensionstructure, in vicinities of beneath the ischial tuberosities are pulleddownward by the second elastic member at least at the time of sitting.Namely, the second elastic member reduces the tension in vicinities ofbeneath the ischial tuberosities at the planar tension structure, ascompared with a case in which the second elastic member is not provided.

Therefore, the support pressure around the pelvis at the planar tensionstructure (the seat cushion) is in the normal line direction, theshearing force applied to the muscles of the seated person is reduced,the seated person is given the impression of a feeling of uniformsupport, and dispersion of (the supporting pressure of) the bodypressure is aimed for. Further, the portions in vicinities of beneaththe ischial tuberosities at the planar tension structure which arepulled downward by the second elastic member, are a structure which isequivalent to a negative spring constant being applied, and thelongitudinal spring constant is small. Therefore, not only the forceapplied to the human body, but also the rate of change of that force(jerking) is decreased. In this way, the absorbability of vibrations isimproved even more, and the comfort of the ride also is improved.

In a seat which is a fourth aspect of the present invention, in the seatwhich is the third aspect of the present invention, the second elasticmember pulls the planar tension structure such that maximum flexing atthe time of sitting arises rearward of a front-rear direction centralportion at the time of sitting.

In the seat which is the fourth aspect of the present invention, due tothe second elastic member pulling the planar tension structure downwardat the time of sitting, maximum flexing of that planar tension structurearises rearward of the front-rear direction central portion. In thisway, the seating posture is stable.

In a seat which is a fifth aspect of the present invention, in the seatwhich is the first aspect of the present invention, the elasticsupporting structure includes a third elastic member which is providedbetween the frame for the sitting portion and the planar tensionstructure, and which, at a time of sitting, pulls rearward portions atouter sides of a pelvis of a seated person at a rear end of the planartension structure.

In the seat which is the fifth aspect of the present invention, theplanar tension structure structures at least a portion of the cushionmaterial of the seat cushion, and the portions, which are at the outersides in the left-right direction of the pelvis at the rear end of theplanar tension structure, are pulled rearward by the third elasticmember at least at the time of sitting. Namely, the third elastic memberincreases the front-rear direction tension of the planar tensionstructure at the outer sides of the pelvis, as compared with a case inwhich the third elastic member is not provided.

Therefore, the portions supporting the femoral regions of the seatedperson at the planar tension structure (the seat cushion) are hightension (i.e., highly rigid), the seated person is given the impressionof a continuous sensation of supporting pressure, and the unsteadysensation (the so-called hammock sensation phenomenon) of that seatedperson is suppressed.

In a seat which is a sixth aspect of the present invention, in the seatwhich is the first aspect of the present invention, the elasticsupporting structure is provided between the frame for the sittingportion and the planar tension structure, and, at a time of sitting,urges downward a portion further rearward than a front-rear directioncentral portion of the planar tension structure, and urges upward aportion further forward than the front-rear direction central portion ofthe planar tension structure.

In the seat which is the sixth aspect of the present invention, due tothe elastic supporting structure, at least at a time of sitting, urgingdownward a portion further rearward than and urging upward a portionfurther forward than the front-rear direction central portion of theplanar tension structure, the elastic supporting structure supports theplanar tension structure such that the directions of tension are inthree dimensions.

Therefore, at the rear portion of the planar tension structure, thetension around the sacral bone of the seated person at the time ofsitting is small as compared with a case in which the elastic supportingstructure is not provided, and the fitting sensation improves. Further,due to this decrease in tension, matching of the compliance of theplanar tension structure (the seat cushion) and the compliance of thehuman body is aimed for, and a reduction in pain and numbness around theischial tuberosities is possible. Moreover, due to this decrease intension, the absorbability of impact vibrations and vibrations of theentire body of the seated person, which are caused by top-bottomdirection vibrations, is improved.

On the other hand, at the front portion of the planar tension structure,because the tension is high and the supporting pressure also is high,the compliance of the planar tension structure (the seat cushion) evenbetter matches the compliance of the human body. In particular, becausethe rear portion at the planar tension structure, which corresponds tothe buttocks of the seated person, flexes downward easily and it is hardfor the front portion to flex upward, forward sliding of the seatedperson is prevented, and the seated posture is stable.

In a seat which is a seventh aspect of the present invention, in theseat which is the first aspect of the present invention, the planartension structure is attached to the frame for the back portion, and theelastic supporting structure pulls forward one end portion of the planartension structure and pulls rearward another end portion of the planartension structure, at different positions with respect to a heightwisedirection.

In the seat which is the seventh aspect of the present invention, at theplanar tension structure, tension fields in three dimensions aregenerated by the elastic supporting structure. In this way, the planarrigidity of the planar tension structure can be made to be high, and thesupport load at the time of sitting can be dispersed by continuouslychanging the spring constant in the pushing direction of the planartension structure, in the heightwise direction and in accordance withthe distribution of the mass of the upper half of the seated person.

In a seat which is an eighth aspect of the present invention, in theseat which is the seventh aspect of the present invention, the planartension structure is structured so as to make integral athree-dimensional tension structure of a front surface side and atwo-dimensional tension structure of a rear surface side, at least at asubstantially central portion in a left-right direction, and the elasticsupporting structure pulls forward one end portion of thetwo-dimensional tension structure, and pulls rearward another endportion of the three-dimensional tension structure.

In a seat which is a ninth aspect of the present invention, the seatwhich is the seventh aspect of the present invention further includes asupporting plate disposed so as to be able to rotate rearward, at aposition substantially corresponding to a pelvis of a seated person; anda tension adjusting mechanism mitigating top-bottom direction tension ofthe planar tension structure, in accordance with an amount of movementwhen the supporting plate is rotated rearward.

In the seat which is the ninth aspect of the present invention, when thesupporting plate rotates, in accordance with the amount of movementthereof, the tension of the planar tension structure decreases.Therefore, even in a case in which impact is inputted to the seat back,because the planar tension structure loosens and the force pushing-outthe seat back forward is lessened, a great impact absorbing effect canbe obtained.

A seat which is a tenth aspect of the present invention comprises: aseat frame having a frame for a sitting portion and a frame for a backportion; a cushion material including a three-dimensional solid knitfabric stretched at the frame for the sitting portion or the frame forthe back portion; and a tension adjusting mechanism adjusting tensionsuch that force in a pushing direction arises at a region of the cushionmaterial that a specific region of a human body pushes at a time ofsitting.

In the seat which is the tenth aspect of the present invention, acushion material which includes a three-dimensional solid knit fabric(including a case in which the cushion material is only athree-dimensional solid knit fabric) is stretched at least one of theframe for the sitting portion and the frame for the back portion. Thecushion material, which is stretched at the frame for the sittingportion, structures the seat cushion which supports the seated personfrom the buttocks to the femoral regions, and the cushion material whichis stretched at the frame for the back portion structures the seat backwhich supports the upper body of the seated person. Further, when aperson sits down, the cushion material stretched at the frame for thesitting portion or the frame for the back portion supports the seatedperson while flexing due to pushing-against force which is based on thebody weight of the seated person.

Here, at the cushion material, due to the tension being adjusted by thetension adjusting mechanism, force in the pushing direction is appliedto the region (hereinafter called the predetermined region) which aspecific region of the human body pushes at the time of sitting (thedirections of tension thereof are in three-dimensions). In other words,the cushion material is a structure which is equivalent to a negativespring constant being applied to the predetermined region. Therefore,the spring constant in the direction of pushing by the human body at thepredetermined region (the planar rigidity at the predetermined region)is small. Thus, the reaction force around the specific region of thehuman body (the supporting pressure by the cushion material) decreases,and pain and numbness in a vicinity of the specific region of the seatedperson decreases. Further, when the spring constant is small asdescribed above, the resonance frequency of the cushion material in theaforementioned pushing direction, which is determined mainly by thatspring constant and the body weight of the seated person, is low, thehigh frequency vibrations transmitted to the seated person markedlydecrease, and the comfort of the ride improves.

On the other hand, if the tension adjusting mechanism is set so as tomake high the tension (planar rigidity) of the portions other than thepredetermined region at the cushion material at the time of sitting(portions corresponding to regions of the human body at which it isdifficult for pain to be caused), stabilizing of the seated posture canbe aimed for while pain and the like of the seated person are reduced asdescribed above. Namely, the cushion material generates tension fieldsconforming to the shape of a human body which is locally high tension,and the so-called hammock sensation phenomenon can be suppressed.

In this way, the seat which is the tenth aspect of the present inventioncan stabilize the seated posture while mitigating pain and numbness ofthe seated person. Namely, matching of the compliance of the cushionmaterial (the seat cushion or the seat back) and the compliance of thehuman body can be aimed for. Note that it suffices for the force in thepushing direction, which is applied to the predetermined region of thecushion material by the aforementioned tension adjusting mechanism, tobe applied at the time of sitting, but may be applied in advance beforesitting.

In a seat which is an eleventh aspect of the present invention, in theseat which is the tenth aspect of the present invention, the tensionadjusting mechanism is structured by a connecting member which connectsthe seat frame and a portion of the cushion material corresponding tothe region that the specific region of the human body pushes, and whichfunctions as an elastic member which generates tensile force at the timeof sitting.

In the seat which is the eleventh aspect of the present invention, thetension adjusting mechanism is structured by the connecting member whichconnects the seat frame and a portion of the cushion materialcorresponding to the region that the specific region of a human bodypushes. At the time of sitting, due to the elasticity thereof, theconnecting member applies tensile force in that pushing direction to theaforementioned predetermined region of the cushion material. At thistime, the connecting member may function as an elastic member forexample, and may also function as a damping member or the like.

In this way, because the tension adjusting mechanism is structuredmerely by connecting the frame and the cushion material by theconnecting member, the spring constant in the aforementioned pushingdirection and the tension fields can be easily set to desiredcharacteristics in accordance with, for example, the elasticcharacteristic, the number, the arrangement, and the like of theconnecting member. Further, as compared with a structure which reducespain or the like of the seated person by the shape or the elasticcharacteristic or the like of the cushion material itself, the desiredspring constant and tension fields corresponding to the specificationsor the like of the seat can be easily obtained, and therefore, thedevelopment cost also can be reduced.

In a seat which is a twelfth aspect of the present invention, in theseat which is the eleventh aspect of the present invention, an urgingmember is provided which urges, in a direction opposite to the pushingdirection by the human body at the time of sitting, a region at thecushion material which region is other than a region which is pulled bythe connecting member.

In the seat which is the twelfth aspect of the present invention, at thetime of sitting, the region at the cushion material, which is other thanthe region which is pulled by the connecting member, is urged by theurging member in the direction opposite to the direction of pushing bythe human body. Therefore, at the cushion material, tension fields whichconform even more to the shape of the human body are generated (thecompliance of the cushion material is made to match the compliance ofthe human body even more), and the so-called hammock sensationphenomenon can be suppressed even more.

In a seat which is a thirteenth aspect of the present invention, in theseat which is the twelfth aspect of the present invention, the urgingmember is structured by a compression spring which is disposed beneaththe cushion material at the frame for the sitting portion or rearward ofthe cushion material at the frame for the back portion.

In the seat which is the thirteenth aspect of the present invention, theurging member is structured by a compression spring which is merelydisposed beneath the cushion material at the frame for the sittingportion or rearward of the cushion material at the frame for the backportion. Therefore, the structure is simple, and setting for making thetension fields of the cushion material conform to the shape of the humanbody is easy.

In a seat which is a fourteenth aspect of the present invention, in theseat which is the twelfth aspect of the present invention, the urgingmember is structured by an extension spring which connects the frame forthe sitting portion or the frame for the back portion and the cushionmaterial.

In the seat which is the fourteenth aspect of the present invention, theurging member is structured by a tension spring which merely connectsthe frame for the sitting portion or the frame for the back portion andthe cushion material. Therefore, the structure is simple, and settingfor making the tension fields of the cushion material conform to theshape of the human body is easy.

A seat which is a fifteenth aspect of the present invention comprises: aframe for a sitting portion; a cushion material including a lower layerportion stretched in a front-rear direction at the frame for the sittingportion, and a surface layer portion layered on the lower layer portionand stretched at the frame for the sitting portion; and a tensionadjusting mechanism connecting connection positions at the lower layerportion in vicinities of beneath ischial tuberosities of a seated personand portions at the frame for the sitting portion which portions arelower than the connection positions, and generating tensile force at atime of sitting.

In the seat which is the fifteenth aspect of the present invention, theseat cushion (sitting portion) is structured by the lower layer portionof the cushion material being stretched in the front-rear direction atthe frame for the sitting portion, and the surface layer portion, whichis layered on the lower layer portion, being stretched at the frame forthe sitting portion.

Further, because the connection positions of the lower layer portion arein vicinities of beneath the ischial tuberosities of the seated person,the longitudinal spring constant in the vicinities of beneath theischial tuberosities at (the lower layer portion of) the cushionmaterial is small, and the reaction force around beneath the ischialtuberosities (the supporting pressure by the cushion material)decreases. In this way, pain or numbness around beneath the ischialtuberosities of the seated person is decreased. Moreover, due to thedecrease in the longitudinal spring constant, the resonance frequency ofthe cushion material in the top-bottom direction, which is determinedmainly by that longitudinal spring constant and the body weight of theseated person, is low, the high frequency vibrations transmitted to theseated person markedly decrease, and the comfort of the ride improves.

On the other hand, because the tensile force of the tension adjustingmechanism is applied as front-rear direction tension in the surfacedirection of the lower layer portion which flexes due to sitting, theplanar rigidity of regions at the cushion material, which pass throughvicinities of beneath the ischial tuberosities and which run along thefront-rear direction except for vicinities of beneath the ischialtuberosities where the aforementioned longitudinal spring constant isreduced, is high. In this way, tension fields conforming to the shape ofthe human body are generated at the cushion material, and it is possibleto suppress the so-called hammock sensation phenomenon and aim forstabilization of the seated posture while reducing pain and the like ofthe seated person.

Moreover, in the present seat, the longitudinal spring constant and thetension fields at the cushion material can be easily set to desiredcharacteristics by the elastic characteristic, the arrangement, and thelike of the tension adjusting mechanism which connects the lower layerportion and the frame for the sitting portion. Therefore, by the simplecombination of the elastic elements and damping elements and the likewhich structure the tension adjusting mechanism, the tension isadjusted, and the desired longitudinal spring constant and tensionfields can be obtained, and the development cost is reduced as comparedwith a structure in which the tension is adjusted by the shape or thestructure of the cushion (the shape of a cushion made of a polyurethanefoam, the stitch structure of a three-dimensional solid knit fabric, orthe like).

In this way, the seat which is the fifteenth aspect of the presentinvention can stabilize the seated posture while mitigating pain andnumbness of the seated person. Namely, matching of the compliance of thecushion material (the seat cushion) and the compliance of the human bodycan be aimed for. Note that it suffices for the tensile force, which isapplied to the connection position of the lower layer portion by theaforementioned tension adjusting mechanism, to be applied at the time ofsitting, but may be applied in advance before sitting.

A seat which is a sixteenth aspect of the present invention comprises: aframe for a back portion; a cushion material including a lower layerportion stretched at the frame for the back portion at a portioncorresponding to a region between a lower side of shoulder blades and alumbar vertebrae region of a seated person, and a surface layer portionlayered on the lower layer portion and stretched at the frame for theback portion; and a tension adjusting mechanism connecting at least oneconnection position at the lower layer portion among a connectionposition further upward than beneath the shoulder blades and aconnection position further downward than the lumbar vertebrae region,and the frame for the back portion, and generating tensile force whichpulls the lower layer portion rearward at a time of sitting.

In the seat which is the sixteenth aspect of the present invention, theseat back (back portion) is structured by the lower layer portion of thecushion material being stretched at the frame for the back portion atthe portion corresponding to the region between beneath the shoulderblades and the lumbar vertebrae region of the seated person, and thesurface layer portion, which is layered on the lower layer portion,being stretched at the frame for the back portion.

When a person sits down on this seat, due to the pushing-against forceby the upper body of that seated person, the surface layer portion andthe lower layer portion flex downward. At this time, the tensionadjusting mechanism, which connects the connection position of the lowerlayer portion and the frame for the sitting portion, generates tensileforce pulling the lower layer portion rearward, and pulls the connectionposition of the lower layer portion rearward (the directions of tensionof the lower layer portion are in three dimensions). In this way,because it is a structure which is equivalent to a negative springconstant being applied to the connection position at the lower layerportion of the cushion material, in a vicinity of that connectionposition at the lower layer portion, the spring constant mainly in thefront-rear direction (the planar rigidity at the connection position inthe direction of pushing by the human body) is small.

Further, the connection position of the lower layer portion is one of orboth of (preferably both of) further upward than beneath the shoulderblades of the seated person and further downward than the lumbervertebrae region. Therefore, the aforementioned spring constant at thecushion material in a vicinity of further upward than beneath theshoulder blades and further downward than the lumber vertebrae region(the buttocks) is small, and the reaction force (the supporting force bythe cushion material) around the shoulder blades or the buttocks isreduced. In this way, pain or numbness in a vicinity of the shoulderblades or a vicinity of the buttocks of the seated person is lessened.

On the other hand, at the region between the lumbar vertebrae region andbeneath the shoulder blades of the seated person, which region is at thelower layer portion and is stretched at the frame for the back portion,the planar rigidity is higher than at further upward than beneath theshoulder blades or further downward than the lumbar vertebrae region,due to the tension which accompanies the sitting. In this way, tensionfields conforming to the shape of the human body are generated at thecushion material, and the so-called hammock sensation phenomenon can besuppressed and stabilization of the seated posture can be aimed for,while pain and the like of the seated person are lessened.

Further, in the present seat, the spring constant and the tension fieldsat the cushion material can be easily set to desired characteristics bythe elastic characteristic, the number, the arrangement, and the like ofthe tension adjusting mechanism. Therefore, by the simple combination ofthe elastic elements and damping elements and the like which structurethe tension adjusting mechanism, the tension is adjusted, and thedesired spring constant and tension fields can be obtained, and thedevelopment cost is reduced as compared with a structure in which thetension is adjusted by the shape or the structure of the cushion (theshape of a cushion made of a polyurethane foam, the stitch structure ofa three-dimensional solid knit fabric, or the like).

In this way, the seat which is the sixteenth aspect of the presentinvention can stabilize the seated posture while mitigating pain andnumbness of the seated person. Namely, matching of the compliance of thecushion material (the seat back) and the compliance of the human bodycan be aimed for. Note that it suffices for the tensile force, which isapplied to the connection position of the lower layer portion by theaforementioned tension adjusting mechanism, to be applied at the time ofsitting, but may be applied in advance before sitting.

Moreover, a seat which is a seventeenth aspect of the present inventioncomprises: a seat frame having a fixed frame, and a movable frameprovided at a rear portion of the fixed frame so as to be able to movein a front-rear direction; a cushion material having a cloth springmaterial whose front end portion is anchored at the fixed frame andwhose rear end portion is anchored at the movable frame, and a surfacelayer portion layered on the cloth spring material and stretched at thefixed frame; an urging member provided between the fixed frame and themovable frame, and, at a time of sitting, urging the movable framerearward and adding tension to the cloth spring material; and a tensionadjusting mechanism connecting connection positions which are at thecloth spring material and are in vicinities of beneath ischialtuberosities of a seated person and are further outward and rearwardthan beneath the ischial tuberosities, and portions at the fixed framewhich portions are further rearward and downward than the connectionpositions, the tension adjusting mechanism generating tensile force atthe time of sitting.

In the seat which is the seventeenth aspect of the present invention,the seat cushion (sitting portion) is formed by the cloth springmaterial spanning between the fixed frame and the movable frame, and thesurface layer portion, which is stretched at the fixed frame, beinglayered on the cloth spring material. Namely, the cloth spring materialstructures the lower layer portion of the cushion material. When aperson sits on this seat cushion and the surface layer portion and thecloth spring material flex downward, the movable frame moves forwardwhile resisting the urging force of the urging member, and this urgingforce is applied to the cloth spring material as tension (e.g., tensionover substantially the entire surface). In this way, owing to the thincloth spring material and the urging member, a good flexing sensation isobtained, and it is possible to make the seat be more compact (thinner)and lighter weight.

Here, because the connection positions of the cloth spring material andthe portions of the fixed frame, which portions are positioned furtherdownward and rearward than those connection positions, are connected bythe tension adjusting mechanism, the cloth spring member, which flexesdownward while the rear end portion thereof is moved forward by themovable frame at the time of sitting, is pulled rearward and downward bythe tensile force of the tension adjusting mechanism at the connectionpositions which are further outward and rearward than beneath theischial tuberosities of the seated person (the directions of tension ofthe cloth spring material are in three dimensions).

Among the tensile force of the tension adjusting mechanism, mainly thecomponent which is directed rearward is applied to the cloth springmaterial as local tension in the front-rear direction, and the planarrigidity of the front-rear, left-right direction regions of the clothspring material (the cushion material) which pass through the vicinitiesbeneath the ischial tuberosities is high, and tension fields conformingto the shape of the human body are generated. On the other hand, amongthe tensile force of the tension adjusting mechanism, mainly thecomponent which is directed downward pulls the connection positions ofthe cloth spring material downward, in other words, applies a negativespring constant to the connection positions, and lowers the longitudinalspring constant in vicinities of those connection positions (the planarrigidity in the direction of pushing by the human body at the connectionpositions).

Further, because the connection positions of the cloth spring materialare in vicinities of beneath the ischial tuberosities of the seatedperson, the longitudinal spring constant is reduced beneath thoseischial tuberosities, and the reaction force (the supporting pressure bythe cushion material) beneath the ischial tuberosities of the seatedperson is reduced. In this way, the seated person is properly supportedby highly rigid surfaces at the cushion material and the seated postureis stable, while pain and numbness around beneath the ischialtuberosities of the seated person are lessened. Namely, in the presentseat, the so-called hammock sensation phenomenon is suppressed.

Moreover, because the longitudinal spring constant in vicinities ofbeneath the ischial tuberosities at the cloth spring material (thecushion material) is small as described above, the resonance frequencyof the cushion material in the top-bottom direction, which is determinedmainly by that longitudinal spring constant and the body weight of theseated person, is low, the high frequency vibrations transmitted to theseated person markedly decrease, and the comfort of the ride improves.Further, because the cloth spring material is pulled, at the connectionpositions thereof, rearward and downward by the tension adjustingmechanism, as compared with a structure in which the tension adjustingmechanism is not provided, the region where the downward flexure thereofis a maximum moves rearward, and forward sliding of the seated person isreliably prevented.

In addition, in the present seat, the longitudinal spring constant atthe cushion material can be easily set to the desired characteristic bythe elastic characteristic, the number, the arrangement, and the like ofthe tension adjusting mechanism which connects the cloth spring materialand the fixed frame. Therefore, by the simple combination of the elasticelements and damping elements and the like which structure the tensionadjusting mechanism, the tension is adjusted, and the desiredlongitudinal spring constant can be obtained, and the development costis reduced as compared with a structure in which the tension is adjustedby the shape or the structure of the cushion (the shape of a cushionmade of a polyurethane foam, the stitch structure of a three-dimensionalsolid knit fabric, or the like).

In this way, the seat which is the seventeenth aspect of the presentinvention can stabilize the seated posture while mitigating pain andnumbness of the seated person. Namely, matching of the compliance of thecushion material (the seat cushion) and the compliance of the human bodycan be aimed for. Note that it suffices for the tensile force, which isapplied to the connection positions of the cloth spring material by theaforementioned tension adjusting mechanism, to be applied at the time ofsitting, but may be applied in advance before sitting.

In a seat which is an eighteenth aspect of the present invention, in theseat which is the seventeenth aspect of the present invention, a pushingmember, which pushes the cloth spring material from a lower side at thetime of sitting, is provided further forward than a front-rear directioncentral portion of the cloth spring material.

In the seat which is the eighteenth aspect of the present invention, atthe time of sitting, the pushing member pushes, from beneath, the clothspring material at a region which is further forward than the front-reardirection central portion of the cloth spring material. Therefore,tension based on this pushing force is applied to the cloth springmaterial, and at the region further forward than the buttocks of theseated person, the supporting pressure of the portion which rises fromthe region of maximum downward flexure of the cloth spring material ishigh. Thus, this rising-up portion where the supporting pressure is highfunctions as a dam, and even more reliably prevents forward sliding ofthe seated person. Namely, the pushing member has a tension adjustingfunction which is separate from the tension adjusting mechanism which isthe seventeenth aspect of the present invention.

In a seat which is a nineteenth aspect of the present invention, in theseat which is the eighteenth aspect of the present invention, thepushing member includes a pushing plate which is formed in a rectangularshape of a width of substantially 100 mm and is disposed in a left-rightdirection of the seat and whose rear end portion is positioned from 250mm to 350 mm forward of the connection positions, and an elastic memberwhich is provided between the pushing plate and the fixed frame.

In the seat which is the nineteenth aspect of the present invention, dueto the elastic member being pushed downward via the pushing plateaccompanying sitting, the pushing member pushes the cloth springmaterial from the lower side by the elastic force of that elasticmember.

Here, because the pushing plate, whose width is substantially 100 mm, isdisposed such that the rear end portion thereof is positioned 250 mm to350 mm further forward than the connection position of the tensionadjusting mechanism to the cloth spring member, a dam is formed in aproper range from the buttocks to the femoral regions of the seatedperson. In this way, forward sliding of the seated person can beprevented even more reliably. Note that it suffices to appropriately setthe rear end position of the pushing plate within the range of 250 mm to350 mm from the connection position, in accordance with the seatingangle or the like.

In a seat which is a twentieth aspect of the present invention, in theseat which is any one of the fifteenth through seventeenth aspects ofthe present invention, at the surface layer portion, portions between aleft-right direction central portion which supports the seated personand left-right direction both end portions, elongate in a left-rightdirection more easily than the central portion and the both endportions.

In the seat which is the twentieth aspect of the present invention, atthe surface layer portion, which is layered on the lower layer portionor the cloth spring material (hereinafter called lower layer portion)and which is stretched at the frame for the sitting portion or the framefor the back portion, due to the portions between the aforementionedcentral portion and both end portions elongating in the left-rightdirection at the time of sitting, they flex the lower layer portion isdownwardly or rearwardly while flexing downwardly or rearwardly.

Here, the surface layer portion is structured such that the portionsbetween the left-right direction central portion and the left-rightdirection both end portions elongate in the left-right direction moreeasily than the central portion and the both end portions. Therefore, atthe time of sitting, they elongate and flex in the left-right directionand flex the lower layer portion, while maintaining high the tension(planar rigidity) of the left-right direction central portion at thecushion material which supports the seated person. In this way, whilethe aforementioned function of reducing the spring constant ismaintained, tension fields which conform even more to the shape of thehuman body are generated at the cushion material, and the seated posturecan be stabilized even more while lessening pain and numbness of theseated person.

In a seat which is a twenty-first aspect of the present invention, inthe seat which is the twentieth aspect of the present invention, theportions between the left-right direction central portion and theleft-right direction both end portions include elastic members whichelongate more easily than the central portion and the both end portions.

In the seat which is the twenty-first aspect of the present invention,the cushion material has, at the portions between the left-rightdirection central portion and the left-right direction both endportions, elastic members which elongate more easily in the left-rightdirection than the central portion and the both end portions. Therefore,with a simple structure, the aforementioned function of generatingtension fields which conform even more to the shape of the human body isrealized.

In a seat which is a twenty-second aspect of the present invention, inthe seat which is the twenty-first aspect of the present invention, theelastic members include a three-dimensional solid knit fabric.

In the seat which is the twenty-second aspect of the present invention,the elastic members, which are disposed between the left-right directioncentral portion and both end portions of the cushion material, arestructured by a three-dimensional solid knit fabric. Therefore, theelastic characteristics of the elastic members can be set in accordancewith the stitch structure of that three-dimensional solid knit fabric.Further, it is possible to simplify the structure of the cushionmaterial by making (a portion which is stretched in the left-rightdirection and which structures at least a portion of) the cushionmaterial be a three-dimensional solid knit fabric on the whole, and bylayering and fixing a material, which is harder to elongate than thethree-dimensional solid knit fabric, on the obverse surface or thereverse surface of the left-right direction central portion and both endportions.

In a seat which is a twenty-third aspect of the present invention, inthe seat which is the twenty-first aspect of the present invention,left-right direction widths of the elastic members vary continuouslyalong a front-rear direction of the frame for the sitting portion or atop-bottom direction of the frame for the back portion.

In the seat which is the twenty-third aspect of the present invention,in the structure in which the cushion material is stretched at the framefor the sitting portion, the widths of the elastic members varycontinuously along the front-rear direction of that frame for thesitting portion, and in the structure in which the cushion material isstretched at the frame for the back portion, the widths of the elasticmembers vary continuously along the top-bottom direction of that framefor the back portion.

Therefore, the left-right direction elongation amounts of the cushionmaterial are different with respect to the front-rear direction of theseat cushion or the top-bottom direction of the seat back, and tensionfields which conform even more to the shape of the human body can begenerated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, a portion of which is cut-away, showingthe overall structure of a vehicle seat relating to an embodiment of thepresent invention.

FIG. 2 is a front view of the vehicle seat relating to the embodiment ofthe present invention.

FIG. 3 is a perspective view showing a frame for a sitting portion and acloth spring material structuring a seat cushion of the vehicle seatrelating to the embodiment of the present invention.

FIG. 4 is a plan view showing the frame for the sitting portion and thecloth spring material structuring the seat cushion of the vehicle seatrelating to the embodiment of the present invention.

FIG. 5 is a rear view showing the frame for the sitting portion and thecloth spring material structuring the seat cushion of the vehicle seatrelating to the embodiment of the present invention.

FIG. 6 is an exploded perspective view of a movable frame portionstructuring the seat cushion of the vehicle seat relating to theembodiment of the present invention.

FIG. 7 is a side view showing a stretched state of the cloth springmaterial structuring the seat cushion of the vehicle seat relating tothe embodiment of the present invention.

FIG. 8 is a diagram for explanation of dimensions of the frame for thesitting portion and the cloth spring material structuring the seatcushion of the vehicle seat relating to the embodiment of the presentinvention.

FIG. 9 is a schematic diagram showing preferable tension fields at theseat cushion of the vehicle seat relating to the embodiment of thepresent invention.

FIG. 10 is a load distribution diagram at the buttocks and femoralregions of a seated person.

FIG. 11 is a rear view showing a stretched state of a cloth springmaterial structuring a seat back of the vehicle seat relating to theembodiment of the present invention.

FIG. 12 is a side view of a back seat of the vehicle seat, as seen witha near-side side frame removed.

FIG. 13 is a front view of the back seat of the vehicle seat.

FIG. 14 is a side view of another back seat of the vehicle seat, as seenwith the near-side side frame removed.

FIG. 15 is a front view of the other back seat of the vehicle seat.

FIG. 16 is an enlarged side view of main portions of the other backseat.

FIG. 17 is a schematic sectional view showing a three-dimensional solidknit fabric used as a cushion member.

FIG. 18 is a schematic diagram showing an example of one ground knitmaterial used in the three-dimensional solid knit fabric.

FIG. 19 is a schematic diagram showing an example of another ground knitmaterial used in the three-dimensional solid knit fabric.

FIGS. 20A through 20E are respectively schematic sectional views of mainportions of the three-dimensional solid knit fabric, showing appliedexamples of a pile portion.

FIG. 21 is a graph showing vibration transmitting characteristics from aportion around an ischial tuberosity to a seated person.

FIG. 22 is a perspective view corresponding to FIG. 3 and showing amodified example of the seat cushion of the vehicle seat relating to theembodiment of the present invention.

FIG. 23 is a side view corresponding to FIG. 7 and showing the modifiedexample of the seat cushion of the vehicle seat relating to theembodiment of the present invention.

FIG. 24 is a front sectional view of a left-right direction half,showing the modified example of the seat cushion of the vehicle seatrelating to the embodiment of the present invention.

BEST MODE FOR IMPLEMENTING THE INVENTION

A vehicle seat 10, which serves as a seat relating to an embodiment ofthe present invention, will be described on the basis of FIGS. 1 through24. Note that arrow UP, arrow LO, arrow FR, arrow RE, arrow RI and arrowLE shown appropriately in the respective drawings respectively denotethe front direction (traveling direction), the rear direction, theupward direction, the downward direction, the rightward direction, andthe leftward direction, with the traveling direction of the vehicle inwhich the vehicle seat 10 is installed being the reference. When up,down, front, rear, right, left are to merely be designated hereinafter,they correspond to the directions of the aforementioned respectivearrows.

In FIG. 1, the overall structure of the vehicle seat 10 is shown in aperspective view, a portion of which is cut away. A front view of thevehicle seat 10 is shown in FIG. 2. As shown in these drawings, thevehicle seat 10 has a seat frame 12. The seat frame 12 is structured tohave a frame 14 for a sitting portion and a frame 16 for a back portion.

Further, by providing a cushion material 18 for the sitting portion atthe frame 14 for the sitting portion, a seat cushion 20 serving as thesitting portion is formed. By providing a cushion material 22 for theback portion at the frame 16 for the back portion, a seat back 24 isformed.

One end (the bottom end) of the frame 16 for the back portion isconnected to one end (the rear end) of the frame 14 for the sittingportion, so as to be rotatable around a supporting shaft 26 (see FIG. 3and FIG. 5) which is disposed along the left-right direction. In thisway, a reclining mechanism, which can rotate the seat back 24 in thefront-rear direction, is formed. Note that detailed description of thereclining mechanism will be omitted.

First, the structure of the seat cushion 20 and the structure of theseat back 24 will be described. Then, a concrete example of athree-dimensional solid knit fabric 110, which structures a portion ofthe cushion materials 18, 22, will be described.

(Structure of Seat Cushion)

As shown in FIGS. 3 through 6, the frame 14 for the sitting portion,which structures the seat cushion 20, has a pair of left and right sideframes 28 which are respectively long in the front-rear direction.Further, the frame 14 for the sitting portion has frame pipes 30, 32which are long in the left-right direction. These frame pipes 30, 32connect the pair of left and right side frames 28 at the front and rearboth end portions, respectively. The front end portion of a cloth springmaterial 68, which will be described later, is anchored on the framepipe 30 which is positioned at the front end of the frame 14 for thesitting portion.

A base plate 34 is fixed to each of the side frames 28. Each base plate34 is positioned at the rear portion of the side frame 28 and is alsofixed to the frame pipe 32. A long hole 36, which is long along thefront-rear, is provided in each base plate 34, and permits front-reardirection sliding while an arm member 44 or an arm member 46, which willbe described later, is inserted therethrough.

A supporting leg portion 38 stands erect from the top surface of eachbase plate 34, further toward the outer side (the side of the side frame28 to which it is fixed) than the long hole 36, and is for anchoring oneend portion of an extension coil spring 78 which will be describedlater. On the other hand, a shaft-supporting leg portion 40 stands erectfrom the bottom surface of each base plate 34, and is forshaft-supporting the arm member 44 or the arm member 46.

Each shaft-supporting leg portion 40 is formed in a substantial “U”shape whose lower side is open in plan view. Leg pieces 40B, 40C, whichare connected by a connecting portion 40A, face one another in theleft-right direction with the long hole 36 therebetween.

Further, the frame 14 for the sitting portion has a movable frameportion 42 which anchors the rear end portion of the cloth springmaterial 68. As shown in FIG. 6 as well, the movable frame portion 42has the pair of left and right arm members 44, 46.

Each of the arm members 44, 46 has a fit-together hole 48 provided atone end portion thereof. Different longitudinal direction end portionsof a connecting pipe 50 are fit with and fixed to the fit-together holes48. Namely, the arm members 44, 46 are structured so as to be connectedvia the connecting pipe 50 while facing one another, and rotateintegrally while resisting the torsional load of a torsion bar 62 whichwill be described later.

The connecting pipe 50 is formed to be shorter than the frame pipe 30(i.e., the interval between the pair of side frames 28), and the rearend portion of the cloth spring material 68 is anchored thereon.

A boss portion 52 is provided at the other end portion of the arm member44. A boss portion 54 is provided at the other end portion of the armmember 46. A boss hole 52A, through which the torsion bar 62 which willbe described later can be inserted, is provided within the boss portion52. A fit-together hole 54A, which is formed in a non-circular shape asseen in the axial direction, is provided at the arm member 44 side ofthe interior of the boss portion 54, and is for holding one end portionof the torsion bar 62.

On the other hand, a boss hole 54B, through which the torsion bar 62 canbe inserted, is provided continuously with the fit-together hole 54A,within the boss portion 54 at the side opposite the fit-together hole54A. Sleeve members 56, which are formed from a low friction materialsuch as resin or the like, are inserted into the boss holes 52A, 54B.

The movable frame portion 42 is shaft-supported by short shaft members58, 60, which are inserted in the sleeve members 56 in the respectiveboss holes 52A, 54B and which are fixed and attached to the respectivelydifferent shaft-supporting leg portions 40, so as to be able to rotate(swing) around the short shaft members 58, 60 (the boss portions 52,54).

Concretely, in the state in which the arm members 44, 46 are insertedthrough the long holes 36 of the respective base plates 34 and the bossportions 52, 54 are positioned between the leg pieces 40B, 40C of theshaft-supporting leg portions 40, the movable frame portion 42 can swingaround the short shaft members 58, 60 with respect to a fixed portion ofthe frame 14 for the sitting portion, due to the short shaft members 58,60, which are fixed to the leg pieces 40B at the outer sides of theshaft-supporting leg portions 40 and which project within theshaft-supporting leg portions 40, being inserted within the sleevemembers 56 within the respective boss holes 52A, 54B.

Further, in this state, the fit-together holes 48 of the arm members 44,46, i.e., the connecting pipe 50, are positioned further upward than thebase plates 34. Note that a fit-together hole 58A, which is formedsimilarly to the fit-together hole 54A of the boss portion 54, isprovided in the short shaft member 58.

In this way, at the movable frame portion 42, the connecting pipe 50which is positioned above the base plates 34 can rotate (swing) by apredetermined amount in directions of approaching and moving away fromthe frame pipe 30 (the front-rear direction). The arrangement anddimensions of the respective long holes 36 and the frame pipe 32 aredetermined such that the long holes 36 and the frame pipe 32 do notinterfere with the swinging of the movable frame portion 42.

Note that, as shown by the solid line in FIG. 7, the movable frameportion 42 is disposed such that, at a time of not sitting on the seatcushion 20, the connecting pipe 50 is tilted rearward so as to befurthest away from the frame pipe 30, within the aforementionedpredetermined range of rotation. Hereinafter, the position of themovable frame portion 42 at this time will be called the initialposition.

Further, as shown in FIG. 6, the torsion bar 62 is provided between theshort shaft member 58 and the short shaft member 60 which are fixed tothe shaft-supporting leg portions 40. The torsion bar 62 is a solidcylindrical member at which is generated a torsional load which isproportional to the amount of twisting. The both longitudinal directionend portions of the torsion bar 62 are made to be non-circularconfigurations (detent configurations) in sectional view, incorrespondence with the fit-together holes 54A, 58A.

One end portion of the torsion bar 62 is fit-together with thefit-together hole 54A formed in the boss portion 54 of the arm member46, and rotates integrally with this boss portion 54. On the other hand,the other end portion of the torsion bar 62 is fit-together with thefit-together hole 58A of the short shaft member 58, and is unable torotate with respect to the frame 14 for the sitting portion. Note thatthe torsion bar 62 passes through through-holes which are formed in theleg pieces 40C of the respective shaft-supporting leg portions 40. Theintermediate portion of the torsion bar 62 is coaxially inserted throughand protected within a protective pipe 64 which spans between and isfixed between the left and right leg pieces 40C.

In this way, as shown in FIG. 7, when forward moving force is applied tothe connecting pipe 50, the movable frame portion 42 swings forward fromthe initial position (makes the connecting pipe 50 approach the framepipe 30), while twisting the torsion bar 62 and resisting the torsionalload of the torsion bar 62. Namely, at the frame 14 for the sittingportion, there is the structure that, when the movable frame 42 swingsforward, the urging force based on the torsional load (the restoringforce with respect to the twisting) of the torsion bar 62 acts on themovable frame portion 42 (as tension on the cloth spring material 68whose one end portion is anchored on the connecting pipe 50).

Further, when, for example, vibrations accompanying the driving of thevehicle are inputted to the vehicle seat 10, the movable frame portion42 swings while changing the amount of twisting (load) of the torsionbar 62, and absorbs these vibrations. In order to exhibit this function,the spring constants in the front-rear direction (with respect to thefront-rear direction load) of the torsion bar 62 and extension coilsprings 80, which will be described later, are set to be different fromone another.

Moreover, as shown in FIG. 3, a supporting frame 66, which spans betweenthe pair of left and right side frames 28, is fixed and provided furthertoward the front side than the front-rear direction central portion ofthe frame 14 for the sitting portion. The front-rear direction centralportion of the supporting frame 66 is a concave portion 66A which isrecessed and opens upwardly, and is for supporting the spring loads ofcompression coil springs 84 which will be described later. The detailedarrangement of the supporting frame 66 will be described later.

As described above, the cushion material 18 is provided at theabove-described frame 14 for the sitting portion, so as to structure theseat cushion 20. The cushion material 18 has the cloth spring material68 which structures the lower layer portion thereof. The cloth springmaterial 68 is a two-dimensional knit fabric of a mesh (net) structure.Elongation accompanying internal damping due to tension, and restorationdue to canceling of that tension, are possible.

As shown in a plan view in FIG. 4, in plan view, the cloth springmaterial 68 is formed as if both left and right corner portions of therear end are cut-away from a rectangle which substantially correspondsto the frame 14 for the sitting portion. These cut-away portions arecut-away portions 68A. The left-right direction width of the portion ofthe cloth spring material 68, except for the rear end portion where thecut-away portions 68A are provided, is slightly shorter than the lengthof the frame pipe 30, and the width between the left and right cut-awayportions 68A is slightly shorter than the length of the connecting pipe50.

The front end portion of the cloth spring material 68 is anchored on theframe pipe 30, and the rear end portion thereof is anchored on theconnecting pipe 50. Concretely, one portion of the front end portion ofthe cloth spring material 68 is folded over (trained around the framepipe 30), and this folded-over portion is sewed to the portion which isnot folded-over, so as to be formed in a substantially annular shape.Due to the frame pipe 30 being inserted through this annular portion 70,the front end portion of the cloth spring material 68 is anchored on theframe pipe 30. On the other hand, one portion of the rear end portion ofthe cloth spring material 68 is folded over (trained around theconnecting pipe 50), and this folded-over portion is sewed to theportion which is not folded-over, so as to be formed in a substantiallyannular shape. Due to the connecting pipe 50 being inserted through thisannular portion 72, the rear end portion of the cloth spring material 68is anchored on the connecting pipe 50.

The dimensions of the respective portions are determined such that, inthis state and when the movable frame portion 42 is positioned at theinitial position, the cloth spring material 68 is spread out (providedso as to be stretched weakly) along the horizontal direction. On theother hand, when the cloth spring material 68 flexes downward at thetime of sitting on the seat cushion 20, the cloth spring material 68 issupported by the tension which is based on the torsional load of thetorsion bar 62, while moving the connecting pipe 50 of the movable frameportion 42 forward. Further, this is a structure in which the tension atthis time is small as compared with a case in which the movable frameportion 42 and the torsion bar 62 are not provided (a case in which theother end portion is anchored on a fixed portion of the frame 14 for thesitting portion). Namely, the movable frame portion 42 and the torsionbar 62 exhibit the function of adjusting, in a reducing direction, thetension of the cloth spring material 68 at the time of sitting.

Further, a spring hanging member 74 is provided at the reverse surface(the bottom surface) of the cloth spring material 68 along substantiallythe entire left-right direction width. The spring hanging member 74 isstructured by a steel material which is formed in the shape of a flatplate or a small-diameter solid cylinder which is long in the left-rightdirection, and is for a sensation that a foreign object exists to not befelt at the time of sitting. The spring hanging member 74 is sewn-in atthe cloth spring material 68 further toward the front side than thecutaway portions 68A of the cloth spring material 68.

Concretely, as shown in FIG. 4, in the state in which the spring hangingmember 74 is inserted in a bag-shaped material 76 which is formed of afabric material or the like and is long in the left-right direction andis closed in the front-rear and top-bottom directions, due to thebag-shaped material 76 being sewn to the reverse surface of the clothspring material 68, the bag-shaped material 76 is attached to the clothspring material 76. The bag-shaped material 76 is divided into threeportions in the longitudinal direction, such that the portion positionedat the longitudinal direction central portion is a bag-shaped material76A, and the portions positioned at the both end portions are bag-shapedmaterials 76B.

The bag-shaped material 76A is sewn at the front and rear ends thereofto the reverse surface of the cloth spring material 68, in a state inwhich the bag-shaped material 76A positions the spring hanging member 74at the front end portion thereof, and as shown in FIG. 5, is squeezedabove and below and nips the spring hanging member 74 in the top-bottomdirection. On the other hand, the bag-shaped materials 76B are sewn atthe front and rear ends thereof to the reverse surface of the clothspring material 68, in a state in which the bag-shaped materials 76Bposition the spring hanging member 74 at the rear end portions thereofand the lower portions thereof are slightly loose and are apart from thespring hanging member 74. The arrangement of the spring hanging member74 will be described later.

Other end portions of the plural extension coil springs 78, 80, whoseone end portions are anchored to the frame 14 for the sitting portion,are anchored on the spring hanging member 74. Concretely, at thelongitudinal direction both end portions of the spring hanging member 74which are positioned forward of the cut-away portions 68A, the other endportions of the extension coil springs 78, whose respective one endportions are anchored to the distal ends of the supporting leg portions38 of the frame 14 for the sitting portion, are anchored within thebag-shaped materials 76B. Note that the arrangement of the respectiveextension coil springs 78 will be described later.

Due to the one end portions of the respective extension coil springs 78being anchored on the distal ends of the supporting leg portions 38which are positioned slightly further upward than the connecting pipe 50at the initial position (the rear end portion of the cloth springmaterial 68), at the time of sitting (at the time when the movable frameportion 42 swings), the extension coil springs 78 add tension to theleft-right direction both end portions of the cloth spring material 68.

Namely, at the time of sitting, the extension coil springs 78 have thefunction of adjusting, in the direction of increasing, the tension inthe front-rear direction at the left-right direction both end portionsof the cloth spring material 68, in contrast with the movable frameportion 42 and the torsion bar 62 adjusting, in the direction ofdecreasing, the tension in the front-rear direction at the left-rightdirection central portion of the cloth spring material 68.

On the other hand, the other end portions of the extension coil springs80, whose respective one end portions are anchored on the protectivepipe 64, are anchored on two places of the spring hanging member 74,which two places are symmetrical with respect to the longitudinaldirection central portion and are positioned within the bag-shapedmaterial 76A. Namely, the extension coil springs 80 are disposed so asto be inclined with respect to the top-bottom direction and thefront-rear direction respectively, and so as to be substantiallyorthogonal to the left-right direction (substantially along thefront-rear direction as seen in plan view).

The extension coil springs 80 are structured so as to, in the initialstate of the movable frame portion 42, be in natural states and notgenerate urging force in the pulling direction. Further, as shown inFIG. 7, the extension coil springs 80 are structured so as to, when,accompanying sitting, the movable frame portion 42 rotates forward andmoves the spring hanging member 74 forward, be pulled by the springhanging member 74 and generate urging force (tensile force) indirections oriented rearward and downward and corresponding to theangles of inclination thereof. Note that there may be a structure inwhich the urging forces of the extension coil springs 80 are applied tothe cloth spring material 68 before sitting.

The respective extension coil springs 80 exhibit the function of, bytheir urging forces, adjusting, overall and in the decreasing direction,the tension in the front-rear direction of the cloth spring material 68by pulling the cloth spring material 68 rearward and downward (thedirection of flexing due to sitting). Further, due to mainly therearward-directed components among the urging forces thereof, therespective extension coil springs 80 add, as partial tension and to thecloth spring material 68, tension in the direction substantially alongthe front-rear direction (add it to the aforementioned decreasingtension), at the bag-shaped material 76A side end portions of the leftand right bag-shaped materials 76B which are positioning the springhanging member 74 at the rear end portions thereof (i.e., forward of thebag-shaped materials 76B).

On the other hand, mainly the downward-directed components among theurging forces of the respective extension coil springs 80 apply anegative spring constant to the cloth spring material 68 via the springhanging member 74 (a downwardly-directed spring constant, with respectto the cloth spring material 68 which has an upwardly-directed springconstant). Namely, due to the cloth spring material 68 (the cushionmaterial 18) being pulled downward by the respective extension coilsprings 80, the longitudinal spring constants of the portions to whichthese tensile forces are applied are decreased.

Further, the rearward-downward urging forces of the respective extensioncoil springs 80 regulate the flexing of the cloth spring material 68.Namely, at the time of sitting, the extension coil springs 80 moverearward the regions of the cloth spring material 68 where the maximumflexing downward is generated, as compared with a structure which is notprovided with the extension coil springs 80. Note that the arrangementof the extension coil springs 80 and the bag-shaped material 76 will bedescribed later.

The respective extension coil springs 80 (and the bag-shaped material76B) function as elastic members which generate downward tensile force.Note that the bag-shaped materials 76B can also make the connectingmember exhibit a damping function by, for example, being structured by atwo-dimensional knit fabric which can extend and contract accompanyinginternal damping, in the same way as the cloth spring material 68.

Further, as shown in FIG. 7, a pushing plate 82 and the compression coilsprings 84, which are for applying pushing force to the pushing plate82, are provided below a portion of the cloth spring material 68 whichis further forward than the front-rear direction central portionthereof.

As shown in FIG. 4, the pushing plate 82 is formed in a substantiallyrectangular shape as seen in plan view which is long in the left-rightdirection, and is an elastic member which can bendingly deform in thefront-rear direction. The rigidity of the pushing plate 82 is set so asto obtain a preferable rigid surface arrangement of the cushion material18 which will be described later.

On the other hand, a plurality of (three in the present embodiment) thecompression coil springs 84 are provided, and respective one endportions thereof are anchored within the concave portion 66A of thesupporting frame 66 of the frame 14 for the sitting portion. Thesecompression coil springs 84 are disposed at uniform intervals along theleft-right direction, so as to be symmetrical with respect to aleft-right direction central line of the cloth spring material 68. And,the respective compression coil springs 84 which are positioned at theleft-right direction both ends are disposed further inward than the bothends of a top plate portion 86A which will be described later.

As shown in FIG. 7, the pushing plate 82 is mounted, so as to be unableto fall off, to the other end portions (top end portions) of thesecompression coil springs 84. The pushing plate 82 is structured suchthat, when the movable frame portion 42 is positioned at the initialposition, in the natural states of the respective compression coilsprings 84, the pushing plate 82 is positioned beneath the cloth springmaterial 68 and does not contact the cloth spring material 68. Further,the pushing plate 82 is structured such that, when, accompanyingsitting, the movable frame portion 42 rotates forward and moves thespring hanging member 74 forward, the pushing plate 82 contacts thecloth spring material 68 and compresses the respective compression coilsprings 84, and pushes the cloth spring material 68 (the cushionmaterial 18) upward from beneath due to the elastic forces of therespective compression coil springs 84.

In this way, the pushing plate 82 and the respective compression coilsprings 84 add tension to the cloth spring material 68, and the clothspring material 68, which flexes downward accompanying sitting, forms,at a predetermined position in the front-rear direction, a dam S whichis a portion rising up toward the frame pipe 30. Note that, in thevehicle seat 10 in which the hip point is high and the seating angle issmall, in order to form the dam S at the appropriate position, astructure is preferable in which the pushing plate 82 is made to contactthe cloth spring material 68 in the state before sitting. The dimensionsand arrangement and the like of the pushing plate 82 for forming the damS at the appropriate position will be described later.

Further, returning to FIG. 1, the cushion material 18 has an uppercushion member 86 serving as a “surface skin material” structuring thesurface layer portion of the cushion material 18. This upper cushionmember 86 is structured by the three-dimensional solid knit fabric 110(to be described later) which serves as an elastic member. Further, theupper cushion member 86 is layered on the cloth spring material 68 andis stretched in the left-right direction at the frame 14 for the sittingportion.

Concretely, the front end portion of the upper cushion member 86 isfolded over, and the upper cushion member 86 is stretched between theside frames 28, and is also supported by the frame pipe 30 (or anunillustrated front end frame) which spans between the left and rightside frames 28. Further, the upper cushion member 86 is stretchedbetween the left and right side frames 28 of the frame 14 for thesitting portion at a tension such that the elongation thereof is lessthan 5%.

Further, as shown in FIG. 2, the top plate portion (top surface) 86Awhich is positioned at the left-right direction center of the seatcushion 20 and which the buttocks and femoral regions of the seatedperson contact, a pair of left and right bank portions 86B which arepositioned at the left-right direction both end portions of the topplate portion 86A, and intermediate portions 86C which are respectivelypositioned between the top plate portion 86A and the left and right bankportions 86B, are formed at the upper cushion member 86 (the cushionmaterial 18). The top plate portion 86A, the bank portions 86B, and theintermediate portions 86C are respectively formed along substantiallythe entire front-rear direction length of the seat cushion 20. Further,the bank portions 86B are formed so as to swell further upward than thetop plate portion 86A.

Moreover, the cushion material 18 is provided with a surface skin 88which covers the outer surface of the upper cushion member 86. Thesurface skin 88 is structured by a raw material at which it is difficultfor elongation to arise as compared with, for example, the upper cushionmember 86 (the three-dimensional solid knit fabric 110) of real leatheror the like, and is layered (placed) on the top plate portion 86A andthe bank portions 86B at the upper cushion member 86.

Further, the surface skin 88 is sewn and attached to the upper cushionmember 86 at the left-right direction end portions of the top plateportion 86A and the bank portions 86B (i.e., the end portions of theintermediate portions 86C). In this way, it is easy for the uppercushion member 86 to elongate in the left-right direction at theintermediate portions 86C thereof, and this elongation in the left-rightdirection is regulated by the surface skin 88.

Moreover, the left-right direction widths of the intermediate portions86C of the upper cushion member 86 are changed continuously along thefront-rear direction, so as to be maxima (extremely large) at positionsin the front-rear direction which correspond to positions Z beneath theischial tuberosities of the seated person. In this way, the uppercushion member 86 (the cushion material 18) is structured so as to bethe most easy to elongate in the left-right direction (easy to flexdownwardly at the time of sitting) at the positions Z of the ischialtuberosities. Note that the positions Z beneath the ischial tuberositieswill be described later.

Here, generally, in order to stabilize the seated posture whilemitigating pain and the like of the seated person at the seat, it ispreferable to make the compliance of the seat cushion 20 conform to(match) the compliance of the human body (the seated person).Incidentally, among human bodies, individual differences are great, andthe physical abilities and seated postures are also different, and theways of handling seating over a long time period are also different.Further, the respective regions of a human body show a three-dimensionalconfiguration and are structured by many parameters. Among theseparameters, individual differences are great especially with respect tothe dynamic characteristic of the muscles. Moreover, at the respectiveregions of a human body, the respective parameters vary in accordancewith the shaking of the human body due to the behavior of the vehiclewhile traveling.

Thus, in the seat cushion 20 having the upper cushion member 86 which isstructured by the three-dimensional solid knit fabric 110 and isstretched at the frame 14 for the sitting portion, in order to make thecompliance of the seat cushion 20 conform to the varying compliance of ahuman body, it is desirable to support the cloth spring material 68 sothat the directions of tension are in three dimensions, and to vary thecompliance of the seat cushion 20 on the basis of various types ofparameters of the cloth spring material 68. In this way, a good feel,fitting sensation, bottoming sensation, and stroke sensation, whichcontribute to stabilizing the seated posture while mitigating pain andthe like of the seated person at the seat cushion 20, are created.

As parameters at the cloth spring material 68 for making the complianceof the seat cushion 20 conform to the varying compliance of the humanbody, there are the tension in the tangent direction (the surfacedirection), the elastic force (restoring force) and damping force in thenormal line direction, the planar rigidity which varies in accordancewith the surface area over which pressure is applied by the human body,and the nonuniform tension fields arising due to the supportingstructure of the cloth spring material 68. Further, more concretely, thetension fields at the cushion material 18 at the time of sitting arepreferably set as shown in FIG. 9 on the basis of the aforementionedrespective parameters.

Namely, by setting the tension at regions A at the left and right bothsides of the cushion material 18 and the tension at region B in theleft-right direction and further forward than the ischial tuberositiesZ, to be higher than the tensions at region C and region D respectively,the front-rear direction and left-right direction movement of the seatedperson on the seat cushion 20 can be suppressed. Namely, region C has alower tension than region A and region B, in order to aim forcomprehensive compliance matching with human bodies structured byskeletons and by skin and muscles and having different compliances. Inthis way, at bone protruding portions such as the sacral bone region andthe ischial regions and the like, deformation which is greater than theperipheral portions arises locally at the cushion member 18 (the tensionstructure), but at the peripheral portions of the bone protrudingportions where muscles occupy the majority, deformation which is greaterthan the cushion characteristic which approximates the muscles does notarise. Due to these characteristics, comprehensive compliance matchingbetween the human body and the cushion material 18 (the tensionstructure) is aimed for. Therefore, the offset force (the tangentdirection of the surface) and the pressure (the normal line direction)which are applied to the skin and muscles are reduced, and numbness andpain due to sitting for a long time period can be reduced.

The structure of the above-described seat cushion 20 generates thetension fields shown in FIG. 9 (adjusts the tension) at the cushionmaterial 18 in order to conform to the compliance of the human body. Inorder to suit the shape of a person (a seated person), the respectivestructural elements and the like of the above-described seat cushion 20are formed, arranged, or set at the dimensions expressed hereinafter.Further, these dimensions and the like are set by using the positions Zbeneath the ischial tuberosities as the reference.

As shown in FIG. 10, it is known that the body pressure (supportingpressure) of the seated person is high at vicinities of the positions Zbeneath the ischial tuberosities (e.g., substantially 80% of the bodyweight concentrates in ranges of diameters of 98 mm centered directlybeneath the ischial tuberosities). In this way, the setting of thedimensions of the respective portions structuring the seat cushion 20 byusing the positions Z beneath the ischial tuberosities as a reference,is in order to set the tension fields of FIG. 9 from around the ischialtuberosities to the thighs on the basis of this knowledge.

Here, it is known that an interval W0 between the left and right ischialtuberosities is 100 mm to 115 mm for a Japanese adult male, and is 110mm to 130 mm for a Japanese adult female. Further, in the presentembodiment, as shown in FIG. 7 and FIG. 8, the positions Z beneath theischial tuberosities are set at positions such that a distance L0 in thefront-rear direction from the rear end of the seat cushion 20 (the frontsurface of the lower portion of the seat back 24 at the time of sitting)is substantially 100 mm.

Further, in order to obtain the tension fields of FIG. 9, at the seatcushion 20, it is preferable to set the positions at the cloth springmaterial 68 where the urging forces of the extension coil springs 80 areapplied, to be slightly at the outer sides and at the rear sides of theleft and right positions Z beneath the ischial tuberosities. Therefore,in the present embodiment, as shown in FIG. 8, on the basis of thestandard physique of a Japanese (a height of 170 cm and a slightlylong-torsoed physique), the spring hanging member 74 is disposed at aposition such that a distance L1 rearward from the positions Z beneaththe ischial tuberosities is substantially 30 mm, and the inner side(bag-shaped material 76A side) end portions of the respective bag-shapedmaterials 76B are disposed at positions such that a distance W2outwardly from the position Z beneath the ischial tuberosity at thecorresponding left or right side is substantially 20 mm.

Namely, for example, if the interval W0 between the ischial tuberositiesis set to 110 mm, an interval W3 between the left and right bag-shapedmaterials 76B is substantially 150 mm. Further, an interval W4 betweenthe extension coil springs 80 is 100 mm in the present embodiment. Inthis way, by disposing the respective extension coil springs 80 betweenthe left and right bag-shaped materials 76B in the left-right direction(at the inner side of the interval W4), the tensions due to the rearwardurging forces of the extension coil springs 80 is applied in directionsslightly inclined with respect to the front-rear direction (thedirections in which the legs open) in accordance with the size of theseat and as shown by arrow E and arrow F in FIG. 8, or in rectilineardirections, i.e., the directions corresponding to the regions A in FIG.9. Further, due to this setting, at the region C where the downwardurging forces of the extension coil springs 80 are applied, thelongitudinal spring constant is reduced as described above, and isstructured equivalently to the tension being smaller than at the regionsA.

Note that the settings of these dimensions are adjusted in accordancewith, as one example, the seating angle due to the height of the hippoint of the vehicle seat 10, the design shape, and physiquedifferences. The adjustment width is ±40 mm respectively at distance L1and distance W2 (there may be cases in which the spring hanging member74 is positioned further forward than the positions Z, or the endportions of the bag-shaped materials 76B are positioned between the leftand right ischial tuberosities).

Further, in order to obtain the tension fields of FIG. 9, at the seatcushion 20, the positions at the cloth spring material 68 where theurging forces of the extension coil springs 78 are applied, are set tobe at the left-right direction outer sides of the pelvis of the seatedperson. In this way, the cloth spring material 68 at the time of sittingis structured such that the portions supporting the femoral regions ofthe seated person are high tension.

Further, in order to form the region B (see FIG. 9) of a high tensionsurface of the dam S at the front of the buttocks of the seated person,a front-rear direction length (width) L2 of the pushing plate 82 is madeto be substantially 100 mm, and the pushing plate 82 is disposed suchthat a distance L3 from the spring hanging member 74 to the rear endportion of the pushing plate 82 is within a range from 250 mm to 350 mm.This distance L3 is determined in accordance with the seating angle dueto the hip point. In this way, when, at the time of sitting, the pushingplate 82 pushes the cloth spring material 68 from beneath due to theurging forces of the compression coil springs 84, at the cloth springmaterial 68 which is flexed downward, front-rear direction tension isadded and the planar rigidity (supporting pressure) from the buttocks tothe femoral regions of the seated person becomes high, and the dam S isformed.

In order to prevent the seated person from sliding forward by this damS, it is preferable that the positions Z beneath the ischialtuberosities are positioned in a range of substantially 100 mm or lessrearward of the rear end position of the dam S. Further, in the presentembodiment, in accordance with the fact that the cloth spring material68 is pulled rearward and downward by the urging forces of the extensioncoil springs 80 and the region where the maximum downward flexing arisesat the cloth spring material 68 is moved rearward, as shown by theone-dot chain line in FIG. 7, setting is carried out such that the damS, which is the portion where the cloth spring material 68 rises uptoward the frame pipe 30, is formed at the front side from a position atwhich a distance L4 from the rear end of the seat cushion 20 (the frontsurface of the lower portion of the seat back 24) is substantially 130mm. Namely, in the present embodiment, the dam S is formed from aposition which is substantially 30 mm (L4-L1) forward of the positions Zbeneath the ischial tuberosities.

Further, at the seat cushion 20, as described above, due to the uppercushion member 86 and the surface skin 88 which structure the surfaceportion of the cushion material 18, the upper cushion member 18elongates easily at the left and right intermediate portions 86C, andthe width of the intermediate portions 86C is a maximum at the positionsZ beneath the ischial tuberosities (positions corresponding to thedistance L0 from the rear end of the seat back 24). Therefore, thesurface rigidities of the top plate portion 86A and the bank portions86B are relatively high as compared to the intermediate portions 86C. Inaccordance with the fact that the tension due to the extension coilsprings 80 and the pushing plate 82 is added to the cloth springmaterial 68, the cushion material 18 (the seat cushion 20) is astructure in which there arises tension fields whose directions oftension are in three dimensions.

(Structure of Seat Back)

As shown in FIG. 1, a pair of left and right side frames 90 are providedat the frame 16 for the back portion which structures the seat back 24.The cushion material 22 is stretched between these side frames 90.Further, as shown in a schematic diagram in FIG. 11 as well, wires 92for fixing, which are for attaching a lower cushion member 94 which willbe described later, are provided at the frame 16 for the back portion.

The wires 92 for fixing are structured by upper side wires 92A which arepositioned in a vicinity of the top end at the rear side of the frame 16for the back portion and some of which are suspended between the leftand right side frames 90, intermediate wires 92B which are providedrespectively at the heightwise direction central portions at the rearsides of the left and right side frames 90, and lower side wires 92Cwhich are provided respectively at the lower portions of the left andright side frames 90.

The lower cushion member 94 is stretched at the wires 92 for fixing ofthe frame 16 for the back portion. Concretely, at the rear surface ofthe lower cushion member 94, the left and right both sides of theportion which is lower than the left and right shoulder blades of theseated person, are fixed to the left and right intermediate wires 92B byfixing members 96 respectively. Further, at the rear surface of thelower cushion member 94, the left and right both sides of the portioncorresponding to the lumbar vertebrae region of the seated person arefixed to the left and right lower side wires 92C by the fixing members96 respectively. The fixing members 96 are formed of a material which ishard to elongate as compared with the lower cushion member 94, and havean elastic function and a damping function.

In this way, at the seat back 24, a high rigidity surface is formed fromthe hips of the seated person to the lower side of the shoulder bladesat the time of sitting. On the other hand, by connecting the portionscorresponding to the buttocks and shoulder blades, which jut-out furtherrearward than the hips of the seated person, to the wires 92 for fixingvia extension coil springs 98, the surface rigidities of these portionscorresponding to the buttocks and shoulder blades are set to be low(negative spring constants are applied to these portions, and the springconstants in the front-rear direction of these portions at the time ofsitting are lowered).

Concretely, a spring hanging member 100 formed of a steel material issewn to the lower cushion member 94 in a vicinity of the top end whichis positioned above the portion corresponding to the shoulder blades ofthe seated person. The other end portions of the plural extension coilsprings 98, whose respective one end portions are anchored on the upperside wires 92A, are respectively anchored on the spring hanging member100. In this way, the lower cushion member 94 is elastically connectedto the wires 92 for fixing which are positioned at the rear side of thelower cushion member 94. Similarly to the spring hanging member 74, thespring hanging member 100 is structured so as to not cause the seatedperson to feel a sensation that a foreign object exists.

Further, due to the other end portions of the pair of left and rightextension coil springs 98, whose one end portions are anchored to theleft and right lower side wires 92C respectively, being attacheddirectly at positions corresponding to the buttocks, the lower cushionmember 94 is elastically connected to the wires 92 for fixing which arepositioned at the rear side thereof.

Due to the above, at the seat back 24 as well, the directions of tensionof the lower cushion member 94 are in three dimensions. In the same wayas the seat cushion 20, the lower cushion member 94 is supported by theextension coil springs 98 so that the directions of tension are in threedimensions, in order for the compliance of the seat back 24 to conformto the changing compliance of the human body. Note that, at the lowercushion member 94, the directions of tension before sitting are in threedimensions.

(Concrete Structure of Seat Back)

The concrete structure of the seat back 24 is shown in FIG. 12 and FIG.13. The seat back 24 has the side frames 90, the lower cushion material94, the extension coil springs 98 (98 a, 98 b, 98 c) which anchor thelower cushion material 94 on the side frames 90, and the cushionmaterial 22 of the surface skin.

The lower cushion material 94 is structured by layering athree-dimensional tension structure 94 b on a two-dimensional tensionstructure (cloth spring material) 94 a. The two-dimensional tensionstructure 94 a and the three-dimensional tension structure 94 b are sewnalong the left-right direction central line of the side frames 90 (thespine of the seated person), and are made integral together at thiscentral portion in the left-right direction.

The two-dimensional tension structure 94 a is a two-dimensional knitfabric of a mesh (net) structure. At the two-dimensional tensionstructure 94 a, elongation accompanying internal damping due to tension,and restoration due to canceling of that tension, are possible. As shownin FIG. 13, the two-dimensional tension structure 94 a has two juttingportions 94 a′ which are formed such that the upper end portion of thetwo-dimensional tension structure 94 a, except for the left-rightdirection central portion thereof, juts-out slightly upwardly andoutwardly in the left-right direction. Therefore, the two-dimensionaltension structure 94 a is formed overall in a substantial Y shape.

Respective reinforcing members 95 are sewn and fixed to the top ends ofthe left and right jutting portions 94 a′. One end portions of therespective extension coil springs 98 b are anchored on the reinforcingmembers 95. The other end portions of the respective extension coilsprings 98 b are anchored on an anchor rod 99 which fixedly spansbetween the top ends of the left and right side frames 90 (furtherupward than the top edges of the respective jutting portions 94 a′). Inthe present embodiment, two of the extension coil springs 98 b areprovided at each jutting portion 94 a′ (reinforcing member 95).

Reinforcing members 97 are sewn and fixed to the left and right bothside portions of the two-dimensional tension structure 94 a. One endportions of a plurality of (three each in the present embodiment) theextension coil springs 98 a are anchored on each reinforcing member 97.The other end portions of the respective extension coil springs 98 a areanchored on the front edge portions at the side frames 90. In this way,the two-dimensional tension structure 94 a is stretched at the sideframes 90 so as to be pulled forward.

The reinforcing members 96 are sewn and fixed to the left and right bothside portions of the three-dimensional tension structure 94 b. One endportions of a plurality of (two each in the present embodiment) theextension coil springs 98 c are anchored on each reinforcing member 96.The other end portions of the respective extension coil springs 98 c areanchored on the front-rear direction intermediate portions of the sideframes 90, so that the three-dimensional tension structure 94 b ispulled rearward.

The respective extension coil springs 98 c are disposed between therespective extension coil springs 98 a in the heightwise direction.Namely, the extension coil springs 98 a and the extension coil springs98 c are disposed alternately at different positions with respect to theheightwise direction. In the present embodiment, three of the extensioncoil springs 98 a and two of the extension coil springs 98 c areanchored on each of the left and right side frames 90.

In the vehicle seat 10 having the above-described structure, tensionfields, at which the directions of tension are in three dimensions, aregenerated at the lower cushion material 94. Namely, the forwardpushing-out force, which is applied to the respective portions in theheightwise direction at the left and right both side portions of thetwo-dimensional tension structure 94 a, is reduced (mitigated) orcancelled (offset) by the rearward pushing-out force which is applied tothe three-dimensional tension structure 94 b between these portionswhere the forward pushing-out force is applied. Further, in a steadystate (a state in which there is no change in the load applied to theseat back 24), tension fields in three dimensions arise at the lowercushion material 94. In this way, at the vehicle seat 10, the planarrigidity of the lower cushion material 94 can be increased, and even if,for example, a person of a large build sits at the seat back 24 (theside frames 90) which is wide, the seated person is supported so as tonot have a stooped posture.

Further, at the vehicle seat 10, by supporting the lower cushionmaterial 94 by three-dimensional tension (generating tension fields ofthree dimensions), equivalently, the spring constant in the pushingdirection of the lower cushion material 94 is continuously changed inthe heightwise direction in accordance with the distribution of mass ofthe upper body half of the seated person. In this way, the support loadat the time of sitting can be dispersed.

For example, in a conventional urethane seat, vibrational energytransmitted from the side frames 90 concentrated at load concentrationportions arising due to the lack of correspondence between the shape ofthe urethane (the cushion material) and the shape of the human body. Incontrast, in the vehicle seat 10 of the present embodiment, thevibrational energy, which is transmitted from the side frames 90 via theextension coil springs 98 a, 98 b, 98 c, is absorbed by the lowercushion material 94 (converted into frictional force of thetwo-dimensional tension structure 94 a and the three dimensional tensionstructure 94 b, and consumed), and thereafter, is inputted to the humanbody as vibration in accordance with the load distribution. Accordingly,vibrations which are sensed bodily by the seated person are greatlyreduced, and the comfort of the ride improves.

Further, at the vehicle seat 10, when impact vibrations are inputted tothe seat back 24, the elongation of the extension coil springs 98 abecomes great with respect to the force in the pushing direction(rearward), and the tension of the two-dimensional tension structure 94a increases. On the other hand, because the extension coil springs 98 c,which support the three-dimensional tension structure 94 b, contract,the tension of the three-dimensional tension structure 94 b decreases.As a result, deformation of the three-dimensional tension structure 94 bitself, which is at the side near to the human body, becomes large, andthe absorption of vibrations by the lower cushion material 94 becomeslarge.

Moreover, when the two-dimensional tension structure 94 a is displacedforward past the initial position before sitting while pushing-out thehuman body forward by the repulsion force of the extension coil springs98 a which support the two-dimensional tension structure 94 a, theforces of the extension coil springs 98 c, which pull-back thethree-dimensional tension structure 94 b rearward, are applied (becomerelatively large). Therefore, the forward pushing-out force which isapplied to the human body is abruptly reduced. Namely, the force, whichis attempting to swing-return the human body forward, is abruptlymitigated in the step of that swinging-returning, and the amount ofswinging-returning (overshooting) of the human body past the initialposition before the input of impact is reduced.

In this way, because the lower cushion material 94 is supported by theabove-described three-dimensional tension, the lower cushion material 94has a non-linear elastic characteristic or damping characteristic.Accordingly, for example, even in a case in which a rearward impactpushing force is applied to the back rest by the swinging of the humanbody which accompanies riding-over a protrusion or a step, at thevehicle seat 10, the swinging of the human body can be convergedpromptly by the lower cushion material 94, and the comfort of the ridecan be improved.

(Other Concrete Structures of Seat Back)

The structure of a seat back 24A will be described by using FIG. 14through FIG. 16. Note that the same reference numerals are applied toregions which are the same as the above-described regions, and detaileddescription of these regions will be omitted.

Compared with the seat back 24 shown in FIG. 12 and FIG. 13, the seatback 24A differs mainly with respect to the point that the seat back 24Ahas a rotatable pelvis plate 101.

As shown in FIG. 16, the lower edge portion of the two-dimensionaltension structure 94 a is trained about and anchored on the lower endportion of the pelvis plate 101 which can rotate with respect to theside frames 90. By rotating in the direction of arrow C, the pelvisplate 101 moves the lower end portion thereof substantially upward. Inthis way, the two-dimensional tension structure 94 a rotates the pelvisplate 101 in the direction of arrow C, while twisting the torsion bar bythe tension thereof. Further, due to the rotation of the pelvis plate101 in the direction of arrow C, the two-dimensional tension structure94 a loosens, and the tension thereof is decreased.

In this way, the two-dimensional tension structure 94 a of the seat back24A is anchored on the movable portion of the pelvis plate mechanism 62which is a tension adjusting mechanism. In this way, when the pelvisplate 101 rotates in the direction of arrow C, the tension of thetwo-dimensional tension structure 94 a decreases in accordance with theamount of movement thereof. Therefore, even in a case in which an impactis inputted to the seat back 24A, the pelvis plate 101 is rotated in thedirection of arrow C by the tension (flexing) applied to thetwo-dimensional tension structure 94 a.

Namely, at the vehicle seat 10, even in a case in which an impact isinputted to the seat back 24A, because the two-dimensional tensionstructure 94 a loosens and the pushing-out force toward the front of theseat back 24A decreases, a great impact absorbing effect can beobtained. Further, even in a case in which load accompanying an impactis inputted to (the position of the seat back 24A corresponding to) thepelvis plate 101 from the hips (buttocks) of the seated person via thelower cushion member 94 and the pelvis plate 101 directly rotates in thedirection of arrow C due to this load, the two-dimensional tensionstructure 94 a loosens in accordance with the amount of movementthereof, and a great impact absorbing effect can be obtained in the sameway as in the above-described case.

(Cushion Material)

Further, returning to FIG. 1, the cushion material 22 has an uppercushion member 102 serving as a “surface skin material” which structuresthe surface layer portion of the cushion material 22. This upper cushionmember 102 is structured by the three-dimensional solid knit fabric 110(to be described later) serving as an elastic member. Further, the uppercushion member 102 is layered on the lower cushion member 94 and isstretched between the side frames 90 at a tension such that theelongation thereof is less than 5%. Moreover, the upper cushion member102 goes around the top end of the frame 16 for the back portion andforms a head rest 104.

Moreover, as shown in FIG. 2, a back rest 102A which is positioned atthe left-right direction center at the seat back 24 and which the upperbody of the seated person contacts, a pair of left and right sidesupport portions 102B which are positioned at the left-right directionboth end portions of the back rest 102A, and intermediate portions 102Cwhich are respectively positioned between the back rest 102A and theleft and right side support portions 102B, are formed at the uppercushion member 102 (the cushion material 22). The back rest 102A, theside support portions 102B, and the intermediate portions 102C arerespectively formed over substantially the entire top-bottom directionlength of the seat back 24 (except for the head rest 104).

The side support portions 102B are formed to project further forwardthan the back rest 102A. Namely, the vehicle seat 10 relating to thepresent embodiment is a bucket-type in which the body of the seatedvehicle occupant enters-in between the pair of left and right sidesupport portions 102B. Note that the head rest 104 is provided at theupper side of the seat back 24 between the side support portions 102B.

The cushion material 22 has a surface skin 106 which covers the outersurface of the upper cushion member 102. In the same way as the surfaceskin 88, the surface skin 106 is structured of a raw material at whichit is difficult for elongation to arise, as compared with, for example,the upper cushion member 102 of real leather or the like. Further, in astate of being layered (placed) on the back rest 102A and the sidesupport portions 102B of the upper cushion member 102, the surface skin106 is sewn and attached to the upper cushion member 102 at theleft-right direction end portions of the back rest 102A and the sidesupport portions 102B (i.e., the end portions of the intermediateportions 102C).

In this way, it is easy for the upper cushion member 102 to elongate inthe left-right direction at the intermediate portions 102C thereof, andthis elongation in the left-right direction is regulated by the surfaceskin 106. Further, the left-right direction widths of the intermediateportions 102C of the upper cushion member 102 are changed continuouslyalong the top-bottom direction. In this way, at the seat back 24 (thecushion material 22), the planar rigidity can be set in accordance withthe widths of the intermediate portions 102C.

In the above-described seat back 24, at the time of sitting, the tension(planar rigidity) in the top-bottom and left-right directions isadjusted due to the lower cushion member 94 being attached to the framefor the back portion by the fixing members 96 or the extension coilsprings 98 in accordance with the regions of contact of the seatedperson. Further, due to the upper cushion member 102 having theintermediate portions 120C and the widths of the intermediate portions102C varying continuously along the top-bottom direction, the tension inthe left-right direction is adjusted, and tension fields arise.Moreover, the present embodiment is set such that, at the seat back 24,the upper body of the seated person is stably supported at the portionwhere the planar rigidity is high from the hips of the seated person tothe lower side of the shoulder blades, and the buttocks and shoulderblades, which project out further than the hips, are supported by a lowrigidity surface (a portion whose spring constant in the front-reardirection is low) and numbness and pain are mitigated.

(Concrete Example of Three-Dimensional Solid Knit Fabric)

Next, an example of the three-dimensional solid knit fabric 110, whichis used as the upper cushion member 86 structuring the cushion material18, and the lower cushion member 94 and the upper cushion member 102structuring the cushion material 22, will be described.

As shown in FIG. 17, the three-dimensional solid knit fabric 110 isstructured by a pair of ground knit fabrics 112, 114 which are disposedso as to be separated from one another, and a pile portion 118 which isformed by a large number of connecting threads 116 which go back andforth between the pair of ground knit fabrics 112, 114 and join the two.

For the one ground knit fabric 112, for example, as shown in FIG. 18,there is used a structure which forms a mesh by a flat, knit fabricweave which is continuous in both the wale direction and the coursedirection, from threads 120 in which short fibers are twisted. Further,the other ground knit fabric 114 forms a honeycomb-shaped mesh fromthreads 122 in which short fibers are twisted. Moreover, the otherground knit fabric 114 is a mesh which is larger than the one groundknit fabric 112. Note that the ground knit fabrics 112, 114 are notlimited to a fine weave or a honeycomb shape, and may be structuresusing mesh-like knit fabric weaves other than these.

As shown in FIG. 17, the connecting threads 116 form the pile portion118 by being knit-in between the ground knit fabrics 112, 114 so as tohold the one ground knit fabric 112 and the other ground knit fabric 114at a predetermined interval. In this way, a predetermined rigidity isimparted to the three-dimensional solid knit fabric 110 which is a meshknit.

The three-dimensional solid knit fabric 110 can provide the requiredstiffness in accordance with the thickness and the like of the groundthreads (the threads 120, 122) which form the ground knit fabrics 112,114, but it is preferable that the ground threads 120, 122 be selectedfrom those in a range in which the knitting work is not difficult.Further, monofilament threads can be used as the ground threads 122,122, but in consideration of the touch and the softness of the feel ofthe surface and the like, multifilament threads or spun threads may beused.

As the connecting threads 116, it is preferable to use monofilamentthreads, and those whose thickness is in a range of 167 decitex to 1110decitex are preferable. With multifilament threads it is not possible toobtain a cushionability that has a good restoring force. Further, whenthe thickness is less than 167 decitex, the stiffness of thethree-dimensional solid knit fabric 110 is low, and when the thicknessis greater than 1110 decitex, it becomes too hard, and the proper amountof cushionability cannot be obtained.

Namely, by using monofilament threads of 167 decitex to 1110 decitex asthe connecting threads 116, the load of the vehicle occupant seated onthe seat can be supported by the deformation of the meshes forming theground knit fabrics 112, 114, and the deformation due to the collapsingor buckling of the connecting threads 116 forming the pile portion 118,and the restoring force of the adjacent connecting threads which imparta spring characteristic to the deformed connecting threads 116, and itis possible to form a soft structure which has a soft springcharacteristic and in which concentration of stress does not occur.

Note that recesses and protrusions may be formed at thethree-dimensional solid knit fabric 110. Namely, the ground knit fabrics112, 114 may be fabrics which are knit such that recesses andprojections arise at the surfaces thereof. When recesses and projectionsare formed, spring elements which are substantially arch-shaped incross-section can be formed at the ground knit fabrics 112, 114, andtherefore, an even softer spring characteristic can be imparted, and astructure having elastic compliance which is substantially equivalent toor greater than the elastic compliance of muscles can be easily formed.Note that the elastic compliance is calculated by (flexingamount)/(average pressure value of surface of contact).

The raw materials of the ground threads 120, 122 and the connectingthreads 116 are not particularly limited, and may be, for example,synthetic fibers or regenerated fibers such as polypropylene, polyester,polyamide, polyacrylonitrile, rayon, or the like, or natural fibers suchas wool, silk, cotton, or the like. These raw materials may be usedsingly, or may be used together in an arbitrary combination. They arepreferably a thermoplastic polyester type fiber exemplified bypolyethylene terephthalate (PET), polybutylene terephthalate (PBT) andthe like, or a polyolefin type fiber exemplified by nylon 6, nylon 66and the like, or a fiber combining two or more types of these fibers.

Further, the thread shapes of the ground threads 120, 122 and theconnecting threads 116 also are not limited to the above description,and threads of round cross-sections or threads of irregularly-shapedcross-sections or the like may be used.

The pile weave of the pile portion 118, which is the way of arrangingthe connecting threads 116 forming the pile portion 118, can beclassified into the types shown in FIG. 20A through FIG. 20E, whenexpressed in the state of viewing, from the side surface, the connectingthreads 116 which connect the respective ground knit fabrics 112, 114.

FIG. 20A and FIG. 20B are straight types in which the connecting threads116 are knit-in substantially perpendicularly between the ground knitfabrics 112, 114. Thereamong, FIG. 20A is a structure which is knitstraight in figure-eights. FIG. 20B is a structure which is knit simplystraight.

Further, FIG. 20C, FIG. 20D, and FIG. 20E show cross types in which theconnecting threads 116 are knit so as to intersect midway along, betweenthe ground knit fabrics 112, 114. Thereamong, FIG. 20C is a structure inwhich the connecting threads 116 are crossed in figure-eights. FIG. 20Dis a structure in which the connecting threads 116 are merely crossed.Further, FIG. 20E is a structure in which the connecting threads 116 aregathered together two-by-two and crossed (double-crossed).

Note that, as shown in FIG. 20C through FIG. 20E, when the connectingthreads 116 intersect one another and are disposed obliquely, ascompared with forms (see FIG. 20A, FIG. 20B) in which the connectingthreads 116 are disposed substantially perpendicularly between theground knit fabrics 112, 114, there is the advantage that a soft springcharacteristic having a large compression rate can be imparted whilemaintaining sufficient restoring force by the buckling strength of therespective connecting threads 116.

At the upper cushion members 86, 102 using the three-dimensional solidknit fabric 110 having such a mesh structure, the spring property issmall, the damping ratio is high, deformation following the physique ofthe vehicle occupant occurs easily, and it is easier to fit.

Note that the above-described structures of the three-dimensional solidknit fabric 110 are examples, and, for example, three-dimensional solidknit fabrics having various types of stitch structures, such as, forexample, stitch structures in which convex portions or concave portions,or ribs or the like are formed in the surface, or the like, can be usedat the upper cushion members 86, 102 and the lower cushion member 94.Further, three-dimensional solid knit fabrics of different stitchstructures may be used in accordance with the application and thefunction. Accordingly, for example, the three-dimensional solid knitfabrics 110 of different stitch structures may be employed at the lowercushion member 94 and the upper cushion member 102. Or, instead of thestructure in which the upper cushion member 86 is provided with thesurface skin 88, the three-dimensional solid knit fabric 110, which hasa stitch structure in which the top plate portion 86A and the bankportions 86B are difficult to elongate as compared with the intermediateportions 86C, may be used.

Next, operation of the present embodiment will be described.

In the vehicle seat 10 having the above-described structure, when aperson sits down, at the seat cushion 20, the seated person who hasentered-in between the bank portions 86B is supported by appropriatesupporting pressure from the buttocks to the femoral regions. At theseat back 24, the seated person who has entered-in between the sidesupport portions 102B is supported by appropriate supporting pressurefrom the buttocks to the shoulder blades.

Concretely, at the seat cushion 20 which is the sitting portion, due tothe sitting, the surface skin 88, upper cushion member 86, and clothspring material 68, which are layered, respectively flex downward. Atthis time, due to the upper cushion member 86 mainly elongating in theleft-right direction while the intermediate portions 86C regulate theamount of elongation by the surface skin 88, the upper cushion member 86flexes downward while maintaining the planar rigidity of the top plateportion 86A.

Further, the maximum elongation in the left-right direction of the uppercushion member 86 arises at a position, in the front-rear direction,corresponding to the positions Z beneath the ischial tuberosities of theseated person which is the maximum width portion of the intermediateportions 86C. Therefore, in vicinities of the portions corresponding tobeneath the ischial tuberosities, the upper cushion member 86 attemptsto flex downward greatly.

On the other hand, when the cloth spring material 68 flexes downward,due to the tension which is added to the cloth spring material 68accompanying this flexing (based on the sitting load), the connectingpipe 50 of the movable frame portion 42 is pulled forward. At this time,the movable frame portion 42 rotates the arm members 44, 46 whiletwisting the torsion bar 62.

In this way, the connecting pipe 50, i.e., the rear end portion of thecloth spring material 68, moves forward. The cloth spring material 68flexes downward greatly while urging force, which is based on thetorsional load of the torsion bar 62, is applied to the left-rightdirection central portion as front-rear direction tension which isadjusted in the direction of decreasing. Accordingly, although the clothspring material 68 is a thin structure, it gives the seated person theimpression of a good flexing sensation (stroke sensation). Inparticular, together with the upper cushion member 86 elongating greatlytoward the left and right in vicinities of beneath the ischialtuberosities, a good flexing sensation (stroke sensation), which did notexist conventionally, is obtained.

At this time, as the rear end portion of the cloth spring material 68,i.e., the spring hanging member 74, moves forward, the extension coilsprings 78 are pulled, and the urging forces of the extension coilsprings 78 increase the front-rear direction tension at the outer sidesof the pelvis. On the other hand, at this time, as the spring hangingmember 74 moves forward, the extension coil springs 80 are pulled, andthe directions of tension of the cloth spring material 68 are in threedimensions.

Further, the urging forces of the extension coil springs 80 are appliedto the cloth spring material 68 via the spring hanging member 74 and thebag-shaped material 76. Among the urging forces of the extension coilsprings 80, mainly the rearward-acting components (components of force)pull the cloth spring material 68 rearward and make the partial tensionsin the directions of arrow E and arrow F in FIG. 8 act on the clothspring material 68. For these reasons, at the cloth spring material 68,the planar rigidity from the buttocks to the femoral regions of theseated person (the portions corresponding to the regions A in FIG. 9)becomes high.

On the other hand, among the urging forces of the extension coil springs80, mainly the downwardly-acting components (components of force) pullthe cloth spring material 68 downward. In this way, the cloth springmaterial 68 is a structure which is equivalent to applying elastic forcebased on a negative spring constant, to the positions of the clothspring material 68 connected to the extension coil springs 80 (theregion where the spring hanging member 74 and the bag-shaped material 76are set). Accordingly, the longitudinal spring constant in vicinities ofthese connected positions becomes small. Thus, the planar rigidity atthe region C becomes lower than the planar rigidity at the regions A.

Further, the cloth spring material 68 is pulled rearward and downward bythe extension coil springs 80, and the position where the maximumdownward flexing thereof arises moves rearward. Further, at this time,at the front portion of the seat cushion 20, due to the cloth springmaterial 68 compressing the compression coil springs 84 via the pushingplate 82, the cloth spring material 68 is pushed upward from below bythe pushing plate 82 on the basis of the urging forces of thecompression coil springs 84. In this way, in front of the buttocks ofthe seated person, the planar rigidity of the cloth spring material 68becomes high.

As described above, at the seat cushion 20 (the cushion material 18),accompanying the sitting, tension adjustment, mainly in the left-rightdirection, of the upper cushion member 86, and tension adjustment,mainly in the front-rear direction, of the cloth spring material 68, areachieved. By the tension fields generated as a result thereof, thepreferable planar rigidity arrangement shown in FIG. 9 is realized, andthe dam S is formed at the preferable position slightly (substantially30 mm in the present embodiment) forward of the positions Z beneath theischial tuberosities.

Forward sliding of the seated person is prevented or suppressed by thedam S. Further, due to the seated person being supported from thebuttocks to the femoral regions at the regions A which are high rigiditysurfaces, front-rear and left-right movement of that seated person issuppressed. For these reasons, at the vehicle seat 10, forward slidingand the hammock sensation, which is the phenomenon that the seatedposture is unstable, are cancelled. On the other hand, because theregion D and the region C, which are other than the regions A, are lowrigidity surfaces, the shearing forces applied to the muscles at theportions of the seated person supported at that region D and region Care reduced, and compression of the blood vessels is suppressed. Inparticular, the shearing force which is applied to the muscles aroundbeneath the ischial tuberosities, which are supported by the region Cand at which the body weight of the seated person concentrates, isreduced, and compression of the blood vessels is suppressed.

Therefore, for example, even in the case of driving for a long timeperiod or the like, interruption in blood circulation, such as numbnessor pain or the like, at around beneath the ischial tuberosities (convexportions) of the seated person is reduced (suppressed) or prevented.

In this way, in the vehicle seat 10 relating to the present embodiment,at the seat cushion 20, the seated posture can be stabilized while painand numbness of the seated person are mitigated.

Namely, because the torsion bar 62 and the movable frame portion 42allow forward movement of the rear end of the cloth spring material 68while adjusting the tension of the cloth spring material 68 in thedecreasing direction, the tension (planar rigidity) around the sacralbone of the seated person is reduced and the fitting sensation isimproved. Further, due to this reduction in tension, as described above,pain and numbness around the ischial tuberosities is reduced. Further,due to this reduction in tension, the absorbability of the impactvibrations and the vibrations of the entire body of the seated person,which are due to top-bottom direction vibrations at the seat cushion 20,is improved. Moreover, due to the extension coil springs 80 which pullthe cloth spring material 68 downward, the supporting pressure aroundthe pelvis is in the normal line direction. Therefore, the shearingforce applied to the muscles of the seated person is reduced, and theseated person is given the impression of a sensation of being uniformlysupported, and dispersion of the body pressure (supporting pressure) isaimed for. In addition, due to the extension coil springs 78 which pullthe cloth spring material 68 rearward, the portions which support thefemoral regions of the seated person are high tension, and therefore,the seated person is given the impression of a continuous sensation ofthe supporting pressure, and the unsteady sensation (the so-calledhammock sensation phenomenon) of that seated person is suppressed.Moreover, due to these tension adjustments being applied relatively, asdescribed above, the cloth spring material 68 is supported by tensionsin directions of three dimensions, and the planar rigidity arrangementof FIG. 9 is realized. In this way, the compliance of the seat cushion20 conforms to the compliance of the seated person, and thestabilization of the seated posture and the mitigation of pain or thelike of the seated person can both be achieved.

Further, at the seat cushion 20, as described above, because thelongitudinal spring constant of the region C is reduced, not only theforce applied to the human body, but also the rate of change of thisforce jerking) is reduced. In this way, the absorbability of vibrationsis improved even more, and the comfort of the ride improves. Namely, thetop-bottom direction resonance frequency (natural frequency) of the seatcushion 20, which is determined mainly by the aforementionedlongitudinal spring constant and the body weight of the seated person,becomes low. Therefore, as shown by the vibration transmittingcharacteristic graph in FIG. 21, as compared with a case in which theextension coil springs 80 are not provided, the high frequencyvibrations which are transmitted to the seated person (the inputamplitude), and vibrations in the region of 5 Hz or more in particular,markedly decrease, and the comfort of the ride in the high frequencyvibration region is greatly improved.

Moreover, at the seat cushion 20, as described above, because adifference in surface rigidities (a difference in tensions) is providedat the region A and at the regions B, C, at the time of sitting, a goodstroke sensation which did not exist conventionally is created. Inparticular, due to the combination of the extension coil springs 80 andthe movable frame portion 42 which rotates while twisting the torsionbar 62 (and while pulling the extension coil springs 78), a good flexingsensation based on a sufficient seating stroke is realized while aimingto make the seat cushion 20 thinner (more compact and light-weight).

On the other hand, at the seat back 24, due to the sitting, the surfaceskin 106, upper cushion member 102, and lower cushion member 94, whichare layered, respectively flex substantially rearward. At this time, dueto the upper cushion member 102 elongating mainly in the left-rightdirection while the intermediate portions 102C thereof regulate theamount of elongation by the surface skin 106, the upper cushion member102 flexes substantially rearward while maintaining the planar rigidityof the back rest 102A.

Further, when the lower cushion member 94 flexes substantially rearward,the planar rigidity becomes high at the portions of the lower cushionmember 94 which correspond to the portion at the lower side of theshoulder blades and the lumbar vertebrae region (hips) which areconnected to the wires 92 for fixing via the fixing members 96. Further,at the portions which correspond to the shoulder blades and the buttockswhich are connected to the wires 92 for fixing via the extension coilsprings 98, a negative spring constant is applied and the planarrigidity becomes low. Namely, the directions of tension of the lowercushion member 94 are in three dimensions.

In this way, at the seat back 24 (the cushion material 22), accompanyingthe sitting, tension adjustment, mainly in the left-right direction, ofthe upper cushion member 102, and tension adjustment, in the top-bottomand front-rear directions, of the lower cushion member 94, are achieved,and by supporting the portion of the seated person from the hips to thelower side of the shoulder blades by a high rigidity surface, left andright movement of the seated person is suppressed. In this way, at thevehicle seat 10, at the seat back 24 as well, the hammock sensation,which is a phenomenon in which the seated posture is unstable, iscancelled. On the other hand, because the buttocks and the shoulderblades, which are regions which project further than the hips of theseated person, are supported by low rigidity surfaces, the shearingforces applied to the muscles around the buttocks and the shoulderblades are reduced, and compression of blood vessels is suppressed.Therefore, for example, even in the case of driving for a long timeperiod or the like, interruption in blood circulation, such as numbnessor pain or the like, at around the buttocks and the shoulder blades ofthe seated person is reduced (suppressed) or prevented.

In this way, in the vehicle seat 10 relating to the present embodiment,at the seat back 24 as well, the seated posture can be stabilized whilepain and numbness of the seated person are mitigated. Namely, thecompliance of the seat back 24 conforms to the compliance of the seatedperson, and stabilization of the seated posture and mitigation of painand the like of the seated person can both be achieved.

As described above, in the vehicle seat 10 which is provided with thecushion materials 18, 22 which are structured so as to include the uppercushion members 86, 102 which are the three-dimensional tension knitfabrics 110 which are stretched at the frame 14 for the sitting portionand the frame 16 for the back portion of the seat frame 12 respectively,by providing an elastic supporting structure or a tension adjustingmechanism, an arbitrary planar rigidity arrangement (portions havingdifferent spring constants in the direction of pushing by the seatedperson) can be set at the seat cushion 20 and the seat back 24. Namely,by making the directions of tension of the cloth spring material 68 andthe lower cushion member 94 be in three dimensions by the elasticsupporting structure or the tension adjusting mechanism, the compliancesof the seat cushion 20 and the seat back 24 can be set so as to conformto the compliance of the seated person.

Further, this tension adjusting mechanism is structured by the clothspring material 68 and the lower cushion member 94 structuring thecushion materials 18, 22 respectively, and the extension coil springs80, 98, the bag-shaped material 76, and the fixing members 96 serving asconnecting members. Further, the elastic supporting structure isstructured by the movable frame portion 42 and the torsion bar 62, andthe extension coil springs 78, 80, 98 serving as first through thirdelastic members. Therefore, the desired rigid surface arrangement, whichcorresponds to the hip points, the seating angle, the design shape, thesupposed physique of the seated person, and the like, can be easilyobtained by (changing) the settings such as the characteristics and theconnection positions, the arrangements, the provided number, and thelike of these connecting members and elastic members. Therefore, in thevehicle seat 10 having the above-described structure, the seatdevelopment cost can be greatly reduced as compared with a conventionalurethane seat. Namely, in a conventional urethane seat, because therigid surface arrangement is set in accordance with the shape of theurethane or the combination of urethanes having differentcharacteristics, there is the need to change the urethane mold and toexamine (test) the planar rigidity arrangement (characteristics) inorder to obtain the needed rigid surface arrangement. In contrast, inthe vehicle seat 10, as described above, the desired rigid surfacearrangement can be easily obtained in accordance with the settings ofthe characteristics and the connection positions, the arrangements, theprovided number, and the like of the connecting members.

Moreover, in the vehicle seat 10, the directions of adjusting thetension are made to be different at the cloth spring material 68 and thelower cushion member 94 which are the lower layer portions of thecushion materials 18, 22, and at the upper cushion members 86, 102 whichare the surface layer portions. Therefore, a good planar rigidityarrangement can be obtained by the generated tension fields thereof.Further, in the seat cushion 20 of the present embodiment, thepreferable planar rigidity arrangement shown in FIG. 9 is realized.

In addition, the upper cushion members 86, 102 realize the function ofadjusting the tension in the left-right direction, by the simplestructure of merely providing the intermediate portions 86C, 102C whichelongate easily in the left-right direction. In particular, by thesimple structure of continuously varying the left-right direction widthsof the intermediate portions 86C, 102C, setting (adjustment) of thetension fields, i.e., the planar rigidity arrangement, is possible, andthis structure contributes to cost reduction and a further decrease inthe development costs.

Next, a seat cushion 130 relating to a modified example of the presentembodiment will be described on the basis of FIG. 22 through FIG. 24.Note that the same reference numerals as in the above-describedembodiment are applied to parts and portions which are basically thesame as the above-described embodiment, and description thereof will beomitted.

As shown in FIG. 22 and FIG. 23, the seat cushion 130 differs from theseat cushion 20 with respect to the point that the seat cushion 130 doesnot have the pushing plate 82 and the compression coil springs 84.Further, at the seat cushion 130, the other end portions of extensioncoil springs 132, whose respective one end portions are anchored on theside frames 28, are anchored at the left-right directions both endportions of the cloth spring material 68 slightly forward of the centralportion in the front-rear and left-right directions. At the time ofsitting, the cloth spring material 68 is pulled upward by the extensioncoil springs 132.

Further, stand members 134 are respectively placed at the front side ofthe central portion in the front-rear and left-right directions, at theleft-right direction both end portions of the cloth spring material 68.The stand members 134 are formed in trapezoidal shapes as seen in sideview, and are disposed such that inclined portions thereof straddle theanchor portions of the extension coil springs 132. Moreover, a pushingplate 136 spans above the left and right stand members 134. In this way,the pushing plate 136 is a structure which easily flexurally deformsdownward at the central portion in the left-right direction.

Moreover, an intermediate cushion member 138, which is formed frompolyurethane foam, is placed at the portion of the cloth spring material68 from the front end portion thereof to the rear end portion of thepushing plate 136. The height of the intermediate cushion member 138 islower than the front half portion on the stand member 134, and theintermediate cushion member 138 is disposed so as to not contact thepushing plate 136 at the time of not sitting (see FIG. 24). Further,when the pushing plate 136 flexes accompanying sitting, the pushingplate 136 pushes the upper cushion member 86 from below, due to urgingforce based on the elastic deformation of the intermediate cushionmember 138, and the restoring force of the pushing plate 136 itself.

Note that, at the front portion, the upper cushion member 86 is layeredon the stand members 134 and the pushing plate 136, and at the highportion, the upper cushion member 86 is layered directly on the clothspring material 68. Further, the rear end portion of the cloth springmaterial 68 is trained around the connecting pipe 50 and anchored on theprotective pipe 64.

In the structure relating to the present modified example, due to theextension coil springs 132 pulling the cloth spring material 68 upwardat the time of sitting, the region where the maximum flexing isgenerated at the cloth spring material 68 can be set to be aroundbeneath the ischial tuberosities. Moreover, in the sacral bone seatedposture, due to changes in the seating angle of the cloth springmaterial 68, rotation of the pelvis is prevented and the seated posturecan be stabilized even more. In addition, the inclined portions of thestand members 134 correspond to the portions of the femoral regionswhere the muscles are insensitive, and the supporting of theseinsensitive regions from in front of beneath the ischial tuberositieslessens the sensation that a foreign object exists due to the frame pipe30 which is the fixed end of the seat cushion 130 front end. On theother hand, due to the active supporting of the front portions of thethighs by the pushing plate 136 and the intermediate cushion member 138,the body pressure is reduced, the seated person is given the impressionof a sensation of uniform and continuous support of the femoral regions,and an odd feeling due to differences in physiques or the posture isabsorbed. The other effects are exactly similar to the seat cushion 20,except for the effects due to the pushing plate 82 and the compressioncoil springs 84.

Note that the above-described embodiment and modified example arepreferable structures in which partial tension (initial tension) isadded to the cloth spring material 68 by the extension coil springs 80.However, the present invention is not limited to this. For example, itmay be a structure in which partial tension (initial tension) is addedat the time of sitting or before sitting, due to a highly-rigid netmaterial (a three-dimensional solid knit fabric or the like) or the likebeing layered on and sewn to the portions, corresponding to the regionsA, of the cloth spring material 68 or the upper cushion member 86. In astructure in which initial tension is added to the upper cushion member86 by a high rigidity net material or the like, it is also possible toform a structure which does not have the cloth spring material 68.Further, the seat back 24 as well can be structured similarly.

Further, the above-described embodiment and modified example arepreferable structures in which both the seat cushion 20 and the seatback 24 have the cushion materials 18, 22 which include thethree-dimensional solid knit fabric 110, but the present invention isnot limited to this. For example, it suffices for the seat cushion 20and the seat back 24 to be structured such that only either one of thecushion materials 18, 22 includes the three-dimensional solid knitfabric 110 which is stretched at the seat frame 12.

Moreover, the above-described embodiment and modified example arestructured such that the compression coil springs 84 or the extensioncoil springs 132, which are urging members which urge the cushionmaterial 18 (the cloth spring material 68) toward the side opposite tothe pushing direction by the human body, are provided only at the seatcushion 20, but the present invention is not limited to this. Forexample, urging members corresponding to the compression coil springs 84or the extension coil springs 132 may be provided at the seat back 24.

In addition, the above-described embodiment and modified example arestructures which apply to the present invention to the vehicle seat 10,but the present invention is not limited to this. The present inventioncan be applied to various types of seats such as, for example, seats formeans of transport such as trains, ships, airplanes, and the like, orchairs for offices, chairs for furniture, or the like.

INDUSTRIAL APPLICABILITY

As described above, the seat relating to the present invention is usedwhen the seating comfort is to be improved.

1. A seat comprising: a sitting portion frame; a cushion material including a lower layer portion stretched in a front-rear direction on the sitting portion frame, and a surface layer portion layered on the lower layer portion and stretched on the sitting portion frame; and a tension adjusting mechanism that connects connection positions of the lower layer portion in to portions of the sitting frame that are lower than the connection positions, the connection positions being provided on the lower layer portion at locations corresponding to locations where ischial tuberosities of a person are located when the person is seated in the seat; wherein: the tension adjusting mechanism generates tensile force at a time when the person sits in the seat; the surface layer portion includes portions between a central portion in a left-right direction which support the seated person and both end portions in the left-right direction, and which elongate in a left-right direction more easily than the central portion and the both end portions; and the portions between the central portion in the left-right direction and both end portions in the left-right direction include elastic members which elongate more easily than the central portion and the both end portions.
 2. The seat of claim 1, wherein the elastic members include a three-dimensional solid knit fabric.
 3. The seat of claim 1, wherein left-right direction widths of the elastic members vary continuously along a front-rear direction of the sitting portion frame or a top-bottom direction of the back portion frame.
 4. A seat comprising: a back portion frame; a cushion material including a lower layer portion stretched on the back portion frame at a portion corresponding to a region between a lower side of shoulder blades and a lumbar vertebrae region of a seated person, and a surface layer portion layered on the lower layer portion and stretched on the back portion frame; and a tension adjusting mechanism that connects at least one connection position of the lower layer portion that is located further upward than beneath the shoulder blades and a connection position further downward than the lumbar vertebrae region to the back portion frame; wherein: the tension adjusting mechanism generates tensile force which pulls the lower layer portion rearward at a time of sitting; the surface layer portion includes portions between a central portion in a left-right direction which support the seated person and both end portions in the left-right direction, and which elongate in a left-right direction more easily than the central portion and the both end portions; and the portions between the central portion in the left-right direction and both end portions in the left-right direction include elastic members which elongate more easily than the central portion and the both end portions.
 5. The seat of claim 4, wherein the elastic members include a three-dimensional solid knit fabric.
 6. The seat of claim 4, wherein left-right direction widths of the elastic members vary continuously along a front-rear direction of the sitting portion frame or a top-bottom direction of the back portion frame.
 7. A seat comprising: a seat frame that includes a fixed frame and a movable frame provided at a rear portion of the fixed frame, the movable frame being able to move in a front-rear direction; a cushion material that includes a cloth spring material with a front end portion that is anchored at the fixed frame and a rear end portion that is anchored at the movable frame, and a surface layer portion layered on the cloth spring material and stretched on the fixed frame; an urging member provided between the fixed frame and the movable frame, the urging member urging the movable frame rearward and adding tension to the cloth spring material at a time when a person sits in the seat; and a tension adjusting mechanism that connects connection positions of the cloth spring material to portions of the fixed frame that are rearward and downward with respect to the connection positions; the connection positions are provided on the cloth spring material at locations outward and rearward with respect to locations where ischial tuberosities of a person are located when the person is seated in the seat; wherein: the tension adjusting mechanism generates tensile force at the time when the person sits in the seat; the surface layer portion includes portions between a central portion in a left-right direction which support the seated person and both end portions in the left-right direction, and which elongate in a left-right direction more easily than the central portion and the both end portions; and the portions between the central portion in the left-right direction and both end portions in the left-right direction include elastic members which elongate more easily than the central portion and the both end portions.
 8. The seat of claim 7, wherein the elastic members include a three-dimensional solid knit fabric.
 9. The seat of claim 7, wherein left-right direction widths of the elastic members vary continuously along a front-rear direction of the sitting portion frame or a top-bottom direction of the back portion frame.
 10. The seat of claim 7, wherein a pushing member, which pushes the cloth spring material from a lower side at the time of sitting, is provided further forward than a front-rear direction central portion of the cloth spring material.
 11. The seat of claim 10, wherein the pushing member includes a pushing plate which is formed in a rectangular shape that includes a width of substantially 100 mm and that is disposed in a left-right direction of the seat and that includes a rear end portion that is positioned from 250 mm to 350 mm forward of the connection positions, and an elastic member which is provided between the pushing plate and the fixed frame.
 12. A seat comprising: a frame; and a sheet of a cloth spring material; wherein: a front end portion of the sheet is attached along its length to a front portion of the frame; a rear end portion of the sheet is attached along its length to a rear portion of the frame; the front portion of the frame is provided so that the front portion of the frame and the front end portion of the sheet remain fixed in location when the seat is in use; the rear portion of the frame comprises a connecting portion and a torsion bar, the connecting portion being rotatable about the torsion bar; the rear end portion of the sheet is attached to the connecting portion so that the rear end portion of the sheet and the connecting portion rotate about the torsion bar against a torsional load of the torsion bar when the seat is in use; and rotation of the connecting portion about the torsion bar causes the location of the rear end portion of the sheet to change both in an up-down direction and a front-rear direction in accordance with a pushing force applied to the sheet so that a planar orientation of the sheet changes.
 13. The seat of claim 12, further comprising: at least one first spring member connected to the frame and to the sheet; wherein: the at least one first spring member is attached to the rear portion of the frame at a location above the connecting portion, the location being fixed when the seat is in use; the at least one first spring member is attached to the sheet at a location forward of the rear end portion of the sheet; the at least one first spring member acts to resist movement of the rear end portion of the sheet toward the front portion of the frame when the seat is in use.
 14. The seat of claim 13, wherein the at least one first spring member comprises at least two extension coil springs attached to the sheet at respective locations equidistant from a center line of the sheet in a left-right direction.
 15. The seat of claim 12, further comprising: at least one second spring member connected to the frame and to the sheet; wherein: the at least one second spring member is attached to the rear portion of the frame at a location below the connecting portion, the location being fixed when the seat is in use; the at least one second spring member is attached to the sheet at a location forward of the rear end portion of the sheet; the at least one second spring member acts to resist movement of the rear end portion of the sheet toward the front portion of the frame when the seat is in use.
 16. The seat of claim 15, wherein the at least one second spring member comprises at least two extension coil springs attached to the sheet at respective locations equidistant from a center line of the sheet in a left-right direction.
 17. The seat of claim 15, wherein the at least one second spring member comprises at least one extension coil spring.
 18. The seat of claim 12, further comprising: a plate member; and at least one third spring member; wherein: the plate member extends along a width of the seat beneath the sheet at a location rearward of the front end portion of the sheet; the at least one third spring member is connected to the frame and the plate member; the at least one third spring member pushes the plate member into a bottom surface of the sheet when the seat is in use.
 19. The seat of claim 18, wherein: the plate member comprises a pushing plate having a substantially rectangular shape when viewed from above and having a major dimension provided in a left-right direction; and the at least one third spring member comprises a plurality of compression coil springs attached to the plate member at uniform intervals in the left-right direction.
 20. The seat of claim 12, further comprising: at least one fourth spring member; wherein: the at least one fourth spring member is connected to a side edge portion of the sheet and a side portion of the frame; the at least one fourth spring member acts to resist movement of the side edge portion of the sheet toward a portion of the frame opposite from the side portion of the frame when the seat is in use.
 21. The seat of claim 12, further comprising: a cushion member; and a surface skin; wherein: the cushion member is provided over a top surface of the sheet; the surface skin is provide over a top surface of the cushion member; and the cushion member comprises a three dimensional solid knit fabric. 